caja-dropbox: update to 1.22

### caja-dropbox 1.22.0

  * fix distcheck about caja_extension_dir
  * Initialize Travis CI support
  * Fix distcheck fail
  * use only Python 3 during the build to complete the migration
  * migrate from python2 to python3 of rst2man.py
  * remove more -u modifier for dropbox-cli

### caja-dropbox 1.21.0

  * Python 3 update for dropbox-cli
  * Add Keywords entry to desktop file
  * Use cross-compilation-safe pkg-config macro.
  * Remove deprecated glib2.0 API calls
  * Use GIR bindings instead of pygtk
  * fix UnicodeWarning when exclude command is used with non-latin args
  * Update to redesigned icons
  * small caja-dropbox.in fixes
  * Add a new "dropbox update" command
  * Unlink files that are going to be replaced by the unpack
  * Validate that Dropbox runs after downloading it
  * Use python-gpg instead of python-gpgme
  * Explicitly load using python2 interpreter
  * Refer to .dropbox-dist in only one place
  * fixed 'exclude command raise UnicodeDecodeError'
  * Avoid reading or writing invalid memory addresses
  * Display link url on status
  * Update dropbox.py with shmodel, proxy, and throttle features.
  * update Copyright year

(gutteridge)