art asset and extensibility update (see discrip)

updated the inventory and slots (personal preference..), added
inventory.xcf overlay for easy changing as a template by the Gimp, and
made TERRAINMAP_BLOCK_SIZE for easy adjusting for larger terrain.png
files
add 157139a from boskee, see addit'l info please...

For some reason windows wont let me do path.join() for folders, so i
have to keep all assets in the main folder.  Any suggestions would be
appreciated.
res folder, modified from boskee

organized now, had ta friend help me to troubleshoot whey a function
worked in linux, and not in windows.  ended up had to re-index the
resources folder.  if we hack this a bit more, as boskee suggested, we
may be able to do skins and texture packs.
Added ore generation on random depth (2).
glass_block and lamp_block

renamed old glass_block to lamp_block, new glass_block.  need to set
item background color to transparent
Merge commit 'f133b07b6becd045ded2c5881e9db026b87dcd0f'

Conflicts:
	blocks.py
	main.py
	resources/textures/inventory.png
	resources/textures/texture.png
	resources/textures/texture.xcf
Merge remote-tracking branch 'avelanarius/master'
Added hardness for some blocks