build: updating HISTORY with notes/updates since last release
## Improvements for v1.5.0 ##
- * autotest
- - increased coverage testing (81% across entire project)
* build
- added support for PlatformIO (https://platformio.org) for embeedded
- development
+ development (thanks, @jcw!)
- incorporated recursive copy() methods to objects to facilitate c++ copy
- constructors for bindings
- - improved support for error codes
+ constructors for bindings; now all objects can be deep copied to a new
+ object with their entire memory and state preserved
+ - added convenience method to malloc and copy memory arrays
+ - improved support for error codes across objects and methods
+ - cleaned up spelling errors across project (thanks, @nowls!)
+ - scrubbed function argument variable names to avoid underscore followed
+ by a capital letter, causing trouble with pre-compiler processing
+ - added basic test to check linking to installed library, incorporating
+ into CI/CD pipelines
+ - added more example programs
+ * autotest
+ - increased coverage testing (81% across entire project)
+ - added the ability to "hammer" a particular test by running repeatedly on
+ incremental seeds to assess specific edge cases (e.g. with random data)
+ - added timer to show execution time for each test and identify areas for
+ speed improvements
+ - added methods for testing spectral response of various fields
+ - added special directory for storing output logs: autotest/logs/
+ * benchmark
+ - replacing old C-based benchmark comparison with simpler python version
+ * dotprod
+ - added support for AVX SIMD in vector dot products (thanks, @vankxr!)
+ * fft
+ - adding macro to allow for aligned memory allocation if FFTW is used
+ (thanks, @nowls!)
+ * filter
+ - added new halfband filter design using Parks-McClellan algorithm and
+ qs1dsearch method to provide as exact a specification as possible
+ - added method to retrieve filter response from coefficients array
+ - dds: adding methods to get/set scale
+ - firhilb, iirhilb: added block processing method
+ - msresamp, resamp: adding method to provide the exact number of output
+ samples with provided input size
+ - msresamp2, resamp2: using better halfband filter design for exact user
+ specifications
+ - resamp: adding methods to get/set scale, fixing filter bank resolution
+ (was hard-coded, now respects user configuration)
+ * framing
+ - framesync64: added methods to set callback and userdata (context)
+ fields, adding support for exporting debugging files for post-analysis
+ as well as python script for processing, adding better estimate of
+ error vector magnitude
+ - msource: added convenience method to recall number of samples generated
+ by each source
+ - ofdmflexframesync: added methods to set callback and userdata (context)
+ fields
+ - qpacketmodem: returning much better estimate of error vector magnitude
+ - qsource: fixed issue with carrier frequency adjustment
+ * optim
+ - added qs1dsearch object to perform quad-section 1-dimensional search:
+ similar to bisection search, but to find potentially non-continuous
+ minimum/maximum of function
## Improvements for v1.4.0 ##
