DOC: Updating operators docstrings
Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

- [X] PR title is "DOC: update the <your-function-or-method> docstring"
- [ ] The validation script passes: `scripts/validate_docstrings.py <your-function-or-method>`
- [X] The PEP8 style check passes: `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] The html version looks good: `python doc/make.py --single <your-function-or-method>`
- [X] It has been proofread on language by another sprint participant

Please include the output of the validation script below between the "```" ticks:

```
################################################################################
####################### Docstring (pandas.DataFrame.gt)  #######################
################################################################################

Wrapper for flexible comparison methods gt

Examples
--------

>>> df1 = pd.DataFrame({'num1': range(1,6),
...                     'num2': range(2,11,2),
...                     'num3': range(1,20,4)})
>>> df1
   num1  num2  num3
0     1     2     1
1     2     4     5
2     3     6     9
3     4     8    13
4     5    10    17
>>> df2 = pd.DataFrame({'num1': range(6,11),
...                     'num2': range(1,10,2),
...                     'num3': range(1,20,4)})
>>> df2
   num1  num2  num3
0     6     1     1
1     7     3     5
2     8     5     9
3     9     7    13
4    10     9    17
>>> df1.gt(df2)
    num1  num2   num3
0  False  True  False
1  False  True  False
2  False  True  False
3  False  True  False
4  False  True  False

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	Closing quotes should be placed in the line after the last text in the docstring (do not close the quotes in the same line as the text, or leave a blank line between the last text and the quotes)
	Use only one blank line to separate sections or paragraphs
	Summary does not end with dot
	No extended summary found
	Errors in parameters section
		Parameters {'other', 'level', 'axis'} not documented
	No returns section found
	See Also section not found

################################################################################
####################### Docstring (pandas.DataFrame.ge)  #######################
################################################################################

Wrapper for flexible comparison methods ge

Examples
--------

>>> df1 = pd.DataFrame({'num1': range(1,6),
...                     'num2': range(2,11,2),
...                     'num3': range(1,20,4)})
>>> df1
   num1  num2  num3
0     1     2     1
1     2     4     5
2     3     6     9
3     4     8    13
4     5    10    17
>>> df2 = pd.DataFrame({'num1': range(6,11),
...                     'num2': range(1,10,2),
...                     'num3': range(1,20,4)})
>>> df2
   num1  num2  num3
0     6     1     1
1     7     3     5
2     8     5     9
3     9     7    13
4    10     9    17
>>> df1.ge(df2)
    num1  num2   num3
0  False  True   True
1  False  True   True
2  False  True   True
3  False  True   True
4  False  True   True

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	Closing quotes should be placed in the line after the last text in the docstring (do not close the quotes in the same line as the text, or leave a blank line between the last text and the quotes)
	Use only one blank line to separate sections or paragraphs
	Summary does not end with dot
	No extended summary found
	Errors in parameters section
		Parameters {'other', 'axis', 'level'} not documented
	No returns section found
	See Also section not found



```
If the validation script still gives errors, but you think there is a good reason to deviate in this case (and there are certainly such cases), please state this explicitly.

This PR follows up on previous attempt: https://github.com/pandas-dev/pandas/pull/20291. Please see discussion.

Specifically, comparison methods in ops.py including `.gt()` and `.ge()` do not have standard docstring like other methods. They use a generalized wrapper summary line. This pull request simply adds examples by conditionally building docstring with examples. General changes include: adding global string variable, __flex_comp_doc_FRAME_ and `if` logic to the method, *_flex_comp_method_FRAME*. 
