Remove partial rendering in StelApp

The original use of this was to make the GUI more reactive on slow
devices.  The current desktop version is not using it, and I don't think
people complain about that, so I guess this is not a needed feature.  I
remove it to clean the code.
Do not set FPS to max when the mouse moves

I think this waste the CPU time, instead we should only consider mouse
moves when they actually touch the GUI.

I was hopping to do this using a signal from the GUI, but since
StelGuiBase does not inherit from QObject, this is unfortunately not
possible.  I guess this is a limitation of the plugin system.
Launchpad automatic translations update.
Launchpad automatic translations update.
Launchpad automatic translations update.
Launchpad automatic translations update.
Do not use QOpenGLfunctions in the core

Qt 5.3 makes it difficult to use QOpenGLfunctions in const methods.  Until they
fix that we better not use them at all and stick to OpenGL ES 2 + ANGLE.

To make sure the proper OpenGL include is used, I added it to the config.h
file.

The plugins also need to be modified to only use OpenGL ES 2.
Remove some more QOpenGLFunctions in the core

The goal of this branch is to get ride of all of them.
Remove all QOpenGLFunctions from the plugins

This means they will probably break on Windows, since they don't use OpenGL ES
2.  Better try to port them to OpenGL ES 2, since it would allow us to use
ANGLE.
sgp4ext.cpp: use math.h asinh

Because including StelUtils generate some warnings on Windows.
Add a comment in PlanetShadows

The code of PlanetShadows seems a bit broken, I would totally remove it but
since I don't really understand it I prefer not touching it for the moment.

Yet, since it does not compile on Windows with ANGLE, I add this comment.  It
would be nice if we could make the code OpenGL ES 2 compatible.
Merge from trunk
update settings for surface brightness option
Initial planet rendering cleanup.

The goal is to move planet rendering code from StelPainter to Planet related
classes, as the code is going to become quite specific when planet shadows
are added back.
Continued refactoring of planet rendering code.

Re-imported most of Jörg's code although most of the shader
is not enabled yet.
Launchpad automatic translations update.
update default settings for eyepiece's field stop value
MeteorShowers plugin : Fix shower search
It was ignoring the date range
Improved English of 3 GUI strings
Re-activated satellite shadow.

It's much faster as it was. Rings are still remaining.
And code needs a good cleaning.