Move skia-monitoring logserver over to being managed by Skia Push.

BUG=skia:

Review URL: https://codereview.chromium.org/800103004
Add details cache to gitinfo

This should speed up the buildbot data ingestion, in which commit
details are repeatedly requested.

BUG=skia:3125

Review URL: https://codereview.chromium.org/790353003
Migrate skia-testing-b to managing logserver vis Skia Push.

BUG=skia:

Review URL: https://codereview.chromium.org/803553003
Convert grains from old install to new skia push.

grainspush branch

BUG=skia:

Review URL: https://codereview.chromium.org/799083002