Add block colour save and load to file

Fixed dimensions other than overworld not displaying.
Fixed exception on saving map to image.
Fixed region code overwriting chunks and corrupting region files.
Changed chunk manager code to use the loaded chunk set to update the
map, rather than calling world.getChunkFromChunkCoords(x, z) for each
chunk.

Unfixed: Large circular map mode is stretched.
Unfixed: Regions sometimes don't load.
Fix regions in texture not updating

Also fix scaling problem when using the large circular map mode.
Fix region file sector overwrite problem

In the get free section function the length of current empty section was
not being reset when a non-empty sector was encountered. This caused the
free section length to appear larger than it actually was.
Add freeze map colours feature.

Also fix region regeneration.
Minor changes to image saving code for AnvilMapper
Fix freeze map colours

Fix a bug when the player presses the freeze map colours button after
changing the texture pack but not regenerating the map.

Add localization info to the key bindings.
Fix crash when run with Torch Levers mod
Add max chunk draw distance feature.

Adding max chunk draw distance was not as simple as I anticipated.
Saving chunks is an infrequent operation, so even if the player was
close enough at one point to 'view' the chunk, by the time the chunk
needs to be saved the player might not be near anymore.

To address this a 'chunk viewed' flag array was added so that when a
chunk is within a certain distance to the player a 'viewed' flag is set.
Then when saving or updating the map only the chunks that have been
viewed are processed.

Also attempt to fix bug with regions not closing fast enough by stopping
MapTexture from increasing the refCount field on regions.
Add GUI options for map size and position
Set default chunk save distance to 128

Used to be 256 but 128 seems a nicer default.
Fix zoom level changing when using nether portal

Now the zoom level only changes when you manually change dimensions in
the map GUI, not when using portals.
Fix map blurring

The blurring was caused by the map texture coordinates not being aligned
to texture pixel boundaries.
Fixed underground map position not changing
Added option to turn off map pixel snapping.

Disabled pixel snapping for circular mode as it has no benefit.

Added some comments.