[Ubuntu Touch UI] Fixes 4 minors things

This pull request fixes 4 minor things which are,

- When opening the timetable results page, there is an error "qrc:///src/gui/ubuntu/TimeTableResultsPage.qml:34: ReferenceError: timetableResultsToolbar is not defined"
- Unable to close backend dialog due to lack of close dialog button thereby forcing the user to select a backend service. For instance, I use 9292ov backend which is right at the bottom of the list. If I open the dialog, then the only way is to scroll all the way and choose 9292ov to close the dialog. Instead I have now added a close button.
- Added keywords to the fahrplan2_ubuntu.desktop file since the term "fahrplan" is german for timetable and is not intuitive enough for non-german speaking users. By adding keywords, the user can search for fahrplan by searching for any of the keywords like travel, train, journey etc etc...(smart search)
- Renamed "Start search" to "Plan my journey" as it is more user friendly
- The whole application UI is black and white. Let's take advantage of that to show actions with colors. For instance, the "Plan my journey" turns green when all the fields have been filled in and grey otherwise.