Update for biolibc API changes

Update for bl_gff_t API streamlining

Biolibc 0.2.2 API updates

Updates for biolibc and libxtend API improvements
Additional improvements to build system and documentation

Updates for evolving library APIs

Updates for libxtend and biolibc API changes
Improvements to build system
Minor bug fixes

Updates for new biolibc API, add extract-genes script

Update to use new biolibc API
Add extract-genes script to generate inputs for feature-view.py
Improve test scripts
Other minor fixes and enhancements

Verified on GRCm38 and 39 mouse GFF3 and MACS2 peaks

Verified reasonable results using peaks from a 2020 mouse study
Numerous optimizations, enhancements and bug fixes
Improved man page
Add command line options for desired peak/feature overlap
Tested on FreeBSD, NetBSD, MacOS, and CentOS 7

First tag for packaging

Basic GFF processing functionality complete. Generates introns and upstream region features.