v0.0.0.55 - Can now build extra droids

Have finally added the ability to build additional droids via the droid maintenance station. Only a few other little changes:-

• Can cycle through multiple droids that are on the same tile and on top of any item.
• Droids and tiles selection now shown.
• Fixed an issue with deleting extra mining stations (miners didn't know where to go,.)
• Fullscreen shortcut key added- F11

Next things to do:-

• Job priority, should be going to closest, not next item in list. 
• Noticed an issue, where if you don't have power, droids will try and charge. They should probably use their last remaining power to build solar panels/connectors (if in build queue). Or at least warn the player if they forget to have power generation.
• Droid maintenance should give an overview of all droids and what they are doing. Obviously maintenance should be one of their jobs, so would like that as new job/status, to keep efficiency of items/structure up to improve performance.

Nick