Remove direct Identity usages.

Move static factory methods into IdentityFactory, and replace
almost every use of Identity with ConfigProvider.

Depends-On: I6a32f3592cb5fc3df99a23eee62ae961ce0fc143
Change-Id: I66b382d54b77ef030d88448e456a83eb98aca216
Reviewed-on: http://gerrit.dmdirc.com/2777
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Update submodules: plugins (new commits)

plugins:
    4751172 Chris Smith <chris@dmdirc.com>
            Remove direct Identity usages.

            Depends-On: I66b382d54b77ef030d88448e456a83eb98aca216
            Gerrit: http://gerrit.dmdirc.com/2776

Change-Id: I45369bdf55b4966aa941ff4256797ab0ad02e305
Few more Identity references.

Change-Id: I120bda4c85a31339180146761791fd341d6d4740
Reviewed-on: http://gerrit.dmdirc.com/2778
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager