Sane rest API rate limit defaults

The previous rate limit defaults were unusable in any deployment.
Rate limiting to 10 POSTS per minute and 50 servers per day seems
to low, especially when we can use quotas to actually limit the amount
of resources a user can consume.

Update docstring to explain what the rate limiting is used for.

Fixes bug 1178529

DocImpact changed default values

Change-Id: I8cc93423f76d9b0a5135adf69babc4ff355a0951
Merge "Sane rest API rate limit defaults"