Added a check to make sure git is installed before doing any modifications on a sdk directory, otherwise it will "corrupt" a working SDK when trying to update it and having it fail. <- Issue found by Saucy_Boi in the discord server.
Added a check to make sure "armory" / "armory/blender" is there when loading the start module during the start/stop of the addon to avoid spamming the console with "No Module named Start" and to help new users debug install issues.
Made messages when downloading the SDK a bit less context dependant
Tested in Windows and Linux.