Add Ubuntu Click package

This adds support for Ubuntu Click packages, which is the new packaging format for the Ubuntu App Store.

There is a script, run_on_device.sh, which compiles and starts fahrplan directly on an attached Ubuntu Phone. The script has an additional parameter -c which creates a click package directly on the phone. This package can directly be uploaded to the store, admittedly currently only by me, as the current packaging holds my id for the store.

As Ubuntu Touch apps run inside an AppArmor environment, the app cannot access the file system, except for a few special folders. However, those folders contain the packager ID, which forces us to store the settings in a directory containing the packagers name.

So I guess we need to decide who wants to be the official Maintainer for fahrplan on Ubuntu Touch. I wouldn't mind taking care of it, but I also don't mind if you want to do it yourself (and be able to change the settings directories names to from mzanetti to smurfy again).

Additionally it changes the SearchPage behavior to fall back to the favorites when the search text field is empty, as discussed in the bug report.

When merging this pull request, please let me know if you want to maintain the Ubuntu touch releases yourself or if I should do that. If you want to do it yourself, please register at the ubuntu software store, change the settings path and manifest file to match your id and commit that. As click packages are not (yet?) signed with any key I think I could build an ARM package for you to upload. Another possibility would be to create an ARM chroot inside your Ubuntu VM to compile it in there. However, your mileage may vary.

Please note that this building hazzle is temporary as the Ubuntu SDK will soon support building arm packages similar to the harmattan one. But we're a bit ahead of the SDK guys :)