Synthesis #1: Adopt utf8mb4 and DBIx::Connector (#79)

Synthesis #1: Adopt utf8mb4 and DBIx::Connector (#79)

* use base to make merging with bmo easier

* Revert "Bug 1497042 - Enclose table names in CREATE queries"

This reverts commit 62d5637a4c96abbcde6f308421d676a0336d8e25.

* refactor Bugzilla::DB to not subclass DBI

* use DBIx::Connector to manage database connections

* Ensure we always call DBIx::Connector->dbh before any DBI method

The code didn't allow a way of doing this without a lot of work.

So I had to take the following approach:
The 'dbh' attribute is now a method that delegates to DBIx::Connector's dbh
method. Per the docs, ->dbh() "Returns the connection's database handle. It will
use a an existing handle if there is one, if the process has not been forked or
a new thread spawned, and if the database is pingable. Otherwise, it will
instantiate, cache, and return a new handle."

Then there is the matter of the 'handles' on dbh. I've used Package::Stash to
insert proxy methods into the class when it is loaded.

* Bug 1328659 - Add support for utf8=utf8mb4 (switches to dynamic/compressed row format, and changes charset to utf8mb4)

* add deps

* add prepare_cached to the list of delegated methods.

This was added in bug 340160

* improve the migration to compressed/dynamic rows, skip views

* add missing semicolon

* remove pre-utf8mb4 emoji support

* fix small issue

* add debugging fatal error