Signed-off-by: Ivan Ivlev <iviv@etersoft.ru>

This change adds a 'db' attribute to the `Bugzilla::DB::Schema` class.
In two places (`get_empty_schema` and `deserialize_abstract`) the invocant
argument was called `$class` but was never actually a class. Those were renamed
to `$self`. It was fortunate that they were always objects because otherwise it
would have been more difficult to ensure a `db` is always present.

The Bugzilla::DB object has a qi attribute which returns a special hashref
that can be used inside double-quoted strings to quote database identifiers.

```perl
  my $q = Bugzilla->dbh->qi;
  Bugzilla->dbh->do("SELECT COUNT(*) FROM $q->{groups}");
```

This changes the Schema classes enough so they use Moo, which will allow adding a weak reference to the database connection

Bugzilla::DB::Schema->new() was both a normal constructor and also a
class-loading factory method. It is simpler to just do the class loading at the
call-site (in Bugzilla::DB::_bz_schema).

It's not very likely extensions relied on this behavior so this should be a good
change.

Changed "make all" to "convert" in line no. 359

* use base to make merging with bmo easier

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

This reverts commit 62d5637a.

* 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

Add viewport meta to improve rendering on mobile devices. Without this meta Google Search tools would report Bugzilla pages as not suitable for mobile devices.

Add productive_time = work_time if productive_time is not defined, add ability for adding time equals zero