frontend: Add SNR approximation in dB for VU+ Solo2 NIMs.

Thanks to jacques1971 for the percentage data. The approximation
might improve with more data, currently it's a very loose
approximation.
Fix intermittent missing first character in plugindescription
MediaPlayer: Do not show inforbar when going to menu
Display remaining time since an event was aired as negative.

Signed-off-by: Littlesat <littlesat99@yahoo.com>
On all screens: Move from green to key_green etc.

Signed-off-by: Littlesat <littlesat99@yahoo.com>
Give the About screen a label on the green button.

Signed-off-by: Littlesat <littlesat99@yahoo.com>
MessageBox: Add possibility to get more choices than only yes/no

In addition remove a whitespace. Now you can give a list with options.
Could e.g. later be used to add save timeshift as recording at the
Timeshift protection.
Adjustments for more choices of Messagebox at skin_default.xml
Limit choices visiable at once to 5 for MessageBox

As there is limited space on a screen...
And also center it in hight.
Simplify the Sleeptimer.
Remove inactivity timer setting from userinterface setting

As it is currently available in SleeptimerEdit
MediaPlayer: Add exit protection

Because I thought it was enoying it just quits with exit while you
were watching.
Remove SleepTimerEdit Screen from skin_default.xmk

As it is not required anymore
Only start/stop sleeptimer when the focus is on the sleeptimer

This allows you to change the inactivity timer without starting or
stopping the sleeptimer.
SleepTimerEdit: Remove a not required line of code
SleepTimerEdit: Make the abort handling correctly
SleepTimerEdit: Made the previous commit a bit less complicated

Sorry I copied the incorrect file previously...
SleepTimerEdit: Better clarification how to start/stop Sleeptimer

Add to the description that you need to select the sleeptimer entry
to actually start/stop the sleeptimer
And fix one small unrequired space.
GMEPG: implement day skip in event list

Simplistic implementation of skipping a days worth of events using
the fast forward and rewind keys.
Depending on the value of time_epoch the skip may or may not be
a complete day...
GMEPG: get date back on the time line

I really missed the date in the timeline labels. Looking
up and donw in the event data area made me tired...

So this code brings the old behaviour back into a configure setting.

This basically makes d73dd2b0487400195d139c9f8f6f7c773221ef47 an
optional feature.