Split up the djblets.db.fields module into submodules.
Review Request #9751 — Created March 7, 2018 and submitted
djblets.db.fieldswas getting far too large to easily maintain, and
some upcoming work on
RelationCounterFieldwas going to make that just
a bit harder. This change addresses this by splitting up the different
areas of responsibility into their own submodules.
None of the actual code has changed, and this means the older fields are
still poorly documented. An upcoming change will address this and other
Djblets and Review Board unit tests pass.
Built the docs and made sure that the
linked to the appropriate submodule docs, without serving up its own
copies of the docs.