[12371] Some small changes

* Replace Expansion related magic numbers
* Remove an unneeded double line. Thanks to Ambal for pointing
* Add additional check for DK starting zones map file

Signed-off-by: Schmoozerd <schmoozerd@cmangos>
Remove another redundant InBattleGround() check
[12372] fix Singleton compile error on clang

some members of Singleton were implicitly specialized in the static function
definitions, which conflicted with the initialization of said members (clang
saw it as a redefinition of the specialization)

Signed-off-by: DasBlub <DasBlub@gmail.com>
[12373] fix clang compile error from implicit type conversion

Signed-off-by: DasBlub <DasBlub@gmail.com>
[12374] fix clang compile error from call of templated member function

Signed-off-by: DasBlub <DasBlub@gmail.com>