[scm metrics] Remove old sql builder in Commits class
[query builder] Refactor GetSQLxxxFrom in SCM methods to use self.identities_db
instead of passing the parameter to the method
[mls] Refactor MLS query builders to use the attribute self.identities_db
instead of using the parameter from the method.
[mls] Fix minor errors in mls metrics
[its] Refactor ITS query builders to use the attribute self.identities_db
    instead of using the parameter from the method.
[scr] Refactor SCR query builders to use the attribute self.identities_db
        instead of using the parameter from the method.
[irc] Remove wrong method calls to GetSQLReportFrom