Refactor buildPath() calls in StorageHandler

This is a small leftover from the gsoc_backpack branch merge.
* Added static imports where I thought they were useful. The only thing
  I couldn't really decide was whether to make a static import for
  BUFFER_8K, so I left it as is. For the rest of the file, the context
  is clear and makes the code more readable.
* Changed the preferences of when to use star imports. I was the one who
  changed it from 99 to 5. I see now how that was a mistake and it is
  hereby corrected.
Remove redudandent code in ScriptActivity

Leftover from gsoc_backpack, this is covered by BaseActivity.
Move BackPackActivity to the other activities
A Fragment is a Fragment is a Fragment
Merge pull request #713 from Catrobat/gsoc_backpack_leftovers

GSoC backpack leftovers