Quick Fix for the autoassign in both tau missions now won't swap units mid mission

All missions have now been updated with objectives and images for all the units
Changes have been made to the defence mission added an secondary objective

Bug fixing

Adding images to tau vs imperium mission
working on adding objective markers and images to all missions

Added new tau mission

Bug fixes / Better objectives markers and instructions currently WIP.

Added new mission
Bug fixes with some of the other missions

Fixed issues with Space Marine Assault map with units moving over mountains and hopefully improved pathing with enemy units.

Added a new Imperial Fist missions as well as tweaking the defense mission. As well as fixing up file names to be easier to read and adding preview images to each of the missions

Added New defence Mission and Fixed autoassigned issues with Boarding Map

Updated second mission to allow user to control Iron Fists as they spawn in