Codemirror: Debian installation, fixes, additions

 * file permissions fixed (many non-executables files were marked as executable)
 * remove .git* files from `src/editor/libs/codemirror/` to avoid them from being installed in the system
 * fix installation of icons
 * add Debian folder
 * add command line options and manpage (copied from master branch)

~~The files in `src/editor/libs/codemirror/bin/` are using the interpreter line `#!/usr/bin/env node` which triggers a Lintian warning. Is that the correct interpreter for those scripts?~~

 * changed `#!/usr/bin/env node` in the scripts in `src/editor/libs/codemirror/bin/` to `#!/usr/bin/js`, which is provided by the nodejs package on Ubuntu 12.04-14.10. Also added Lintian overrides.