- Qt plugins and libraries (and associated files) bundled only if necessary
    - Dependencies corrected (for Ubuntu 14.04 and 16.04, at least),
    mostly manually for now
    - run.sh sets Qt plugin path environment variable (=> qt.conf
    no longer needed; removed)

Just commented out the line since I'm not 100% sure it can be removed
(though I can't find a case where it is useful)

- Separated building and packaging
- OpenBoard is now installed in /opt/openboard instead of
/usr/local/OpenBoard-$VERSION/
- Placed a shortcut to run.sh in /usr/bin (so it can be executed with
the `openboard` command)
- Corrected .deb control files to avoid warnings e.g when installing via
software center on Ubuntu
- Added xdg bindings so that .ubz files are recognized and opened
automatically with OpenBoard

- Moved the release scripts into their own folder to clean up the
repository root a bit

(Merge branch 'new-release-script-linux' into dev)

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

- Fixed permissions of qt libs and plugins
- Added some missing plugins (and maybe a couple too many)
- Dependency list is built automatically, while excluding qt libs

- Separated build and package
- OpenBoard now installs in /opt
- All binaries are stripped, for smaller package size

also added error handling and displaying to the user.

Credit: Jaroslav Ryník

I can't get the mobile site to display correctly; the position of the
contents moves around depending on the widget's position on the board.

Switched back to the desktop site because it's not worth spending days
on this.

Credit: Jaroslav Ryník

(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