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>