Unify targeting mechanisms for all commands

[Crystalwarrior]

Currently, commands keep re-implementing targeting mechanisms over and over, leading to some commands being able to target by char name, others by OOC name, third only by just the ID, etc. and it's all a big mess.

There should be a unified targeting mechanism that's able to do all kinds of targeting the command could ever want - similar to get_targets - and with ability to supply multiple types of targets as well, rather than just 1. Additionally, all the commands should start using shlex.split(arg) so as to allow arguments with spaces in them.

[Salanto]

Just use the playerID. Is is unique and short to type.