- "Importer" folder renamed "importer"
- corrected detecting of 64bit architecture
- build context file is created in build.sh

also added error handling and displaying to the user.

(widgets' size and position weren't necessarily calculated based on
their current screen, but on the entire desktop geometry)

This also fixes the skewing observed during podcast recording

- Display a meaningful error message to the user when adding or trying
to play a video
- Make sure the video placeholder is visible even after switching pages

(Not doing so resulted in either a trashed item being selected when
returning to board mode, or a crash if the item had been permanently
deleted)

The previous solution didn't really have any effect; only a handful of
settings were in the mUserSettings or mAppSettings at the moment it was
called. The better solution is to just call value() in the constructor
of UBSetting, which means the setting is cached as soon as it is
created.

- Sort by Z before duplicating a selection (so that relative Z's are
kept)
- in UBZLayerController, iterate only through UBGraphicsScene's fast
access items, not QGraphicsScene::items

- Defined constants in UBSettings for highlighter preview circle colors
- Switch between light and dark colors when changing backgrounds
- For eraser: use color settings that were defined in UBSettings (they
were ignored since the preview circle was added)