update version to R21
admin.yell is back since R21

- remove changes from ca533a24226ca557aa2245c98ab3d7f0d9e43293
use 'teamFactionOverride' instead of teamXFactionOverride'

vars.team1FactionOverride, ..., vars.team4FactionOverride was in R19 replaced by 'vars.teamFactionOverride'
Merge pull request #164 from ozon/improvements/bf4_parser

[BF4] R21
XLRstats v3.0.0-beta.3 - Moved minPlayers checking to XLRstats plugin, obsoleted the subPlugin: XLRstatsControllerPlugin
[TESTS] fix mysql test database name cannot be changed
[TESTS] add Drone.io configuration file
[TESTS] fix xlrstats tests
[TESTS] change BF4 test_map_unknown to it does not depend on the existing maps

This help maintaining the tests while new maps are added to the game
add Second Assault DLC GamesModes and Maps

- add 4 new maps
- add CTF game mode
- change tests
Merge pull request #166 from ozon/features/BF4_SecondAssault

[BF4] Second Assault DLC