Issue title: Add post_parse_action parser method for more customization
 Issue body: ## Feature Idea
Add `post_parse_action` parser method for more customization. Entries will be passed through this method after lines are parsed, to add the ability to customize parsers a bit more.
 Comments: 
 Comment 0: Feature is in place in the dev branch, and will be included in the 3.1 release (coming soon).
{'source': 'GithubIssues', 'repo_name_with_owner': 'dogoncouch/logdissect', 'issue_id': 310151821, 'repo_stars': 131.0}