Fixing documentation links, warnings, PEP8 in utils
Fixing documentation links and warnings in units, including units.format.Base in the docs
Merge pull request #2509 from bsipocz/fix_various_docs_links

Fix various docs links
Added nitpick options (still False by default)
Fix API links in astropy.convolution
Added a few more cases to ignore
Fixed a few broken API links
Don’t specify full path for dimensionless_unscaled
Fixed HDF5 intersphinx links
Added more exceptions related to non-public inherited classes