Fix various MySQL version issues with new charset stuff

Summary:
Ref T1191. Notable stuff:

  - Adds `--disable-utf8mb4` to `bin/storage` to make it easier to test what things will (approximately) do on old MySQL. This isn't 100% perfect but should catch all the major stuff. It basically makes us pretend the server is an old server.
  - Require utf8mb4 to dump a quickstart.
  - Fix some issues with quickstart generation, notably special casing the FULLTEXT handling.
  - Add an `--unsafe` flag to `bin/storage adjust` to let it truncate data to fix schemata.
  - Fix some old patches which don't work if the default table charset is utf8mb4.

Test Plan:
  - Dumped a quickstart.
  - Loaded the quickstart with utf8mb4.
  - Loaded the quickstart with `--disable-utf8mb4` (verified that we get binary columns, etc).
  - Adjusted schema with `--disable-utf8mb4` (got a long adjustment with binary columns, some truncation stuff with weird edge case test data).
  - Adjusted schema with `--disable-utf8mb4 --unsafe` (got truncations and clean adjust).
  - Adjusted schema back without `--disable-utf8mb4` (got a long adjustment with utf8mb4 columns, some invalid data on truncated utf8).
  - Adjusted schema without `--disable-utf8mb4`, but with `--unsafe` (got truncations on the invalid data).

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10757