Write Atom.desktop file directly from template

Previously this was written to resources/linux/Atom.desktop
which would create issues when running `sudo script/grunt install`
followed by `script/grunt mkdeb`
Move install file var under if block
Group template variables together
grunt.file.write creates parent dirs
:lipstick:
Write control/desktop files to temp folder
Track temp folders
Write control/desktop files to build dir
Write file using grunt API
:lipstick:
Merge pull request #3031 from atom/ks-copy-desktop-file-during-install

Don't write .deb files in place