Added some new functions and a new file.

Added new file "/player/misc.inc". This contains general player related
functions such as IsPlayerInWater and GetClosestPlayerFromPoint.
Documented with comments.

Edited data/datetime.inc:
Added MsToString
Added RoundTimeStamp
Added TimestampToDateTime
Added GetTickCountDifference

Edited data/misc.inc:
Added TruncateString

All additions/edits are commented.