Quick Save/Load

Adds a new feature
Alt+S for quick saving the current game
Alt+L to load the last quick save
Remove unused strings in English file

Removing these again, not sure why they keep coming back!
Revert "Remove unused strings in English file"

This reverts commit 93c8d58e1353ef271e477a9efeaacfc96e68ed4b.
Key change/addition

Adds two new key presses to the game.  Z to speed up the game (was W in
TH) and on release the previous speed returns.
Moves X from a debug only option, on press the walls become transparent
and return to normal on key release.
Whilst walls are transparent you cannot buy new plots
Merge pull request #1 from MarkL1961/Transpatent-Walls

Transparent walls