Several Bugfixes in EcoCommands

[LordTylus]

• Player cannot pay themselves anymore. This caused client and server to go out of sync, and cause crashes. Also it created money out of thin air.
• All Numbers are now formatted #,##0
• Fixed KeyAlreadyAddedException in Econ Top. 2 Players with same SteamID but different SerialID could break it. Assumption that it has something to do with perma death. The server I saw it on had 2 identities for that person too. One alive one dead.
• !econ check can now also check for offline players.
• !econ pay shows the correct playername in noticiation now instead of the MyPlayer toString()
• !econ give/set/take/reset now inform that the player might be offline.

The last four commands should also work with offline players. But this optimization is not "important" enough. So I didn't bother.

[LordTylus]

@Bishbash777 I highly recommend reviewing the commits individually. I didn't want to merge conflict myself by creating several PRs for the fixes.