NtfLog plugin

General:
-added command permission names to README.txt
-removed a printed message for when a dataContainer is not found for a player
-changed the messages for insufficient altered block input to be more informative (like for using /getblocklog without altering any block that you wish to check)

Bugfixes:
-fixed a bug involving admins with usernames containing capital letters not being able to use /getblocklog
-fixed a bug involving the time based ordering of logged block changes that led to some incorrect rollback/redo results

For memory efficiency, only about 10 changes will be kept for any particular block.*

*The number recorded can actually be a bit higher than 10, since the ceiling for a deletion operation is actually 14 changes. In other words, the system won't actually delete any recorded changes until there are 14 or more changes for a particular block.