Reimplement PAINTOR

[bschilder]

• Now working with echoverse.
• Generalized to any data input type (GWAS/QTL/TWAS)
  to avoid hard-coded args.
• Streamlined functions and reduced clutter.
• Automated installation of PAINTOR. PAINTOR: installation issues #12
• Added unit tests.
• Get/query full PAINTOR annotations Add large annotations echoannot#10
• User-supplied annotations via annot (PAINTOR.R annot param + PAINTOR_prepare_annotations.R)
• xgr/roadmap annotations (PAINTOR.R annot_xgr and annot_roadmap params).

[bschilder]

Currently stuck on the issues of hosting individual files due to a bug in Zenodo:
zenodo/zenodo#2131
Haven't heard back from the Zenodo team in a while.

If Zenodo doesn't work, will upload the files to another public facing server and distribute from there.

[bschilder]

Fixed. PAINTOR fully reimplemented in pure R: PAINTOR.R, PAINTOR_run.R, PAINTOR_prepare_annotations.R (replaces Python 2.7 AnnotateLocus.py), PAINTOR_fetch_annotations.R. Multi-ancestry support added. Commits: 304ff47, de6c833.