Package restructuring and v0.7 support

• Simplified the package structure by merging together the BuildApp and ApplicationBuilder modules.

These are the changes you need to make in your program:

• You should remove using ApplicationBuilder from the source-code of
  programs being built, since the change_dir_if_bundle behavior will
  now come default for all applications. using ApplicationBuilder in
  your program source will cause it to fail to build.
• module BuildApp has been removed. You should remove using BuildApp
  from your build scripts to build with julia v0.7.