Finished adding 15 new blocks, GuiNotificationScreen, ErrorScreen restart button

EXT
-------------------------
Finished:

CUSTOM_BLOCK_SUPPORT_LEVEL
ENV_SET_COLOR
CLICK_DISTANCE
HOLDTHIS
EXT_ADD_ENTITY

Pending:

EXT_INFO
EXT_ENTRY
SET_TEXT_HOTKEY
EXT_REMOVE_PLAYER_NAME
EXT_ADD_PLAYER_NAME

Skipping:

ExtPlayer (Do we need this?)
GroupRank (Not sure HOW to implement this as a functional addition)

Changed:
EXT_ADD_ENTITY (XYZRL) can maybe make a workaround for this
Merge pull request #28 from Jonty800/master

Finished adding 15 new blocks, GuiNotificationScreen, ErrorScreen restar...