This has a whole bunch of changes to AppDetails:

* use MORE Button design from upstream f-droid
* make description text selectable
* remove custom linkify method use system default
* fix nested scrolling problem in description
  * Having a non-scrolling but still clickcable (links + selection)
    TextView is not something we get from Android
  * Short of implementing a rather custom MovementMethod which does
    Selection + Link handling but forbids scrolling (which might be
    possible but it seems tricky to get right)
  * So instead we actually set a short version of the description text
    when the description is in collapsed state. This way there's no
    possibility for scrolling,
  * There's two side-effects I did notice:
    1. Text selection is reset on expand/collapse
    2. I saw subtly different text layout once in expanded/collapsed
       state.
* italic styling for packageId

A couple of things are still not perfect but I couldn't figure our what
was going on there:
* link clicks work but the link doesn't get the selected effect before
  opening.
* selection in app summary, packageid, antifeatures and signature only
  work in landscape mode...

closes #15 (not sure, but I couldn't reproduce it
anymore with these changes)
closes #28