-> also deleted obsolete UBInterpolator classes

We can (again) check for updates and, if an update is available, send
the user to the site to download them.

The old format (a .json specifying a version number and download URL)
was kept. The address for this file is now specified in the settings.

We can (again) check for updates and, if an update is available, send
the user to the site to download them.

The old format (a .json specifying a version number and download URL)
was kept. The address for this file is now specified in the settings.

If enabled in the preferences menu, pen and marker strokes will be
replaced by a simplified stroke after they are drawn.

The algorithm is very basic (for now): if three points are almost lined
up (the threshold angle can be specified in the config file), then the
middle one is removed. This is repeated over the whole stroke; new
polygons are then generated based on the simplified stroke points.

This typically cuts down on number of points and polygons by a factor of
about 10, while having minimal visual impact.

- Added a curveToPolygon function that creates a curved polygon,
eliminating the need to generate lots of small ones to make a curve look
smooth.

- Cleaned up the rest of the code a bit

- UBGraphicsScene calls UBGraphicsStroke::addPoint, which returns a list
of points that can be drawn. It may be none (e.g we discard very small
segments), one (if we do no interpolation) or several.

- Added a UBInterpolator base, abstract class. Various interpolation
methods can be added easily.

- Current methods: Basic spline (custom), Catmull-Rom spline (based on
alglib), and Bézier

- Added a setting to toggle interpolation. Added this to the UI as well

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

Mostly, removal of old code that had been commented out instead of
removed

- Moved all platform-specific code to UBPlatformUtils
- For now, removed support (on Linux) for checking whether onboard is 
running when OpenBoard is started (it wasn't working anyway, but it needs a
cleaner solution for all 3 platforms)

(due to commit 9adc8991).

Fullscreening should now work as expected in OSX 10.9 and 10.10, with
one or multiple monitors.

The project didn't compile on Windows.. list of modifications:

- Added essential changes that hadn't been committed / pushed (Qt4->Qt5
changes; other misc. changes by Abdel)
- Temporarily disabled podcasts, as the modules don't compile with Qt5.2/
5.5

Currently, the application compiles on Windows, with MSVC2010 32-bit

Due to QWidget::showFullScreen having side-effects on OSX (setting the
dock and menubar to autohide, making it impossible to then set them as
hidden), the calls to that method were replaced with
UBPlatformUtils::showFullScreen(QWidget *). This function then calls
QWidget::showMaximized() on OSX, or QWidget::showFullScreen() on Linux
and Windows.

It is currently still impossible to switch smoothly between showing or
hiding the dock on OSX; current behaviour is to hide it all the time,
even in desktop mode.

removed redundant OBCocoa files / namespace; moved functions to UBPlatformUtils, which serves the same purpose

Application compiles and runs, with some caveats. Full list of changes:

- minor changes related to Qt4->Qt5 API differences

- Replaced calls to Carbon framework by Cocoa

- Removed registering of AE event handler. Seems to be done
automatically in Qt5.

- temporarily removed Podcast functionality, pending (presumably)
complete re-write due to Quicktime being obsolete in newer OS X
versions.

- Created OBCocoa namespace, and associated files src/core/OBCocoa.h/.mm, to
handle OS X - specific system calls. Currently used only by
UBApplication, but can in the future provide a useful interface between
the cocoa framework and OB, to avoid having too much OSX-specific code
in various files

Q_WS_MACX -> Q_OS_OSX
Q_WS_MAC -> Q_OS_OSX
Q_WS_WIN -> Q_OS_WIN
Q_WS_X11 -> Q_OS_LINUX