Rationalize main production and noctua / NEO autocomplete index creation (and codebase)

[kltm]

Currently, as an apparent result of #620 (specifically https://github.com/geneontology/amigo/commit/65be1caa3fb2d8c21df81b1337753343e20a28b6 and possibly part of https://github.com/geneontology/amigo/commit/7b4ff9ed294ed3ebaf43d1c9fe37035d77b89f9e from #634).

The fix to this is one of the following:

1. do a mini-refactor so that the default relation is exposed at the config level and have NEO and standard production use different configs
2. if possible (need to check on this) switch the NEO load so that is it using isa_partof instead of regulates, to bring it inline with master and other index creation

In the interim, I'm going to create an AmiGO branch that tracks master except for those two code lines so that @abessiari can continue with Noctua devops testing.