Improve STRICT_ALL_TABLES warning

Summary:
  - Make the warning describe rationale and point at the MySQL manual explicitly.
  - Add a reference to the developer mode config, in case the user wants to resolve the probelm by disabling developer mode.
  - Now that the message is huge, provide a summary.
  - Move from "Database" to "MySQL" setup checks -- this is kind of arbitrary, but the former is used for fatals (pre-install) and the latter for warnings (post-install) right now. This has no practical impact on anything and is purely stylistic.

Test Plan:
{F31798}

{F31799}

Reviewers: edward, blc

Reviewed By: edward

CC: aran

Differential Revision: https://secure.phabricator.com/D4835