Core/Commands: implement .pvpstats command

Shows number of battleground victories in the last 7 days

Closes #13460

Conflicts:
	sql/base/auth_database.sql
	sql/updates/auth/2014_11_10_00_auth.sql
	src/server/game/Accounts/RBAC.h

(cherry picked from commit fd0b96178174e624510a10f5bc27b60af406d901)

sql/updates/auth/2014_11_10_00_auth_from_335.sql

@@ -0,0 +1,7 @@
+DELETE FROM rbac_permissions WHERE id = 797;
+INSERT INTO rbac_permissions (`id`, `name`) VALUES
+(797, 'Command: pvpstats');
+
+DELETE FROM rbac_linked_permissions WHERE `linkedId` = 797;
+INSERT INTO rbac_linked_permissions (`id`, `linkedId`) VALUES
+(199, 797);

sql/updates/world/2014_11_10_04_world.sql

@@ -0,0 +1,8 @@
+DELETE FROM `trinity_string` WHERE entry IN (80, 81);
+INSERT INTO `trinity_string` (`entry`, `content_default`) VALUES 
+(80, 'BattleGround victories in the last 7 days\nAlliance: %d\nHorde: %d'),
+(81, 'BattleGround scores storing is disabled!');
+
+DELETE FROM `command` WHERE `name`='pvpstats';
+INSERT INTO `command` (`name`, `permission`, `help`) VALUES
+('pvpstats', 797, 'Shows number of battleground victories in the last 7 days');