RecordTimer.py: Reset first_try_prepare on repeating timers

See http://openpli.org/forums/topic/30676-problem-with-a-repeated-timers/

Initially 'first_try_prepare' set to True. So, if current channel isn't the
required one, then RecordTimerEntry.activate() switches to the required
channel. But this method also sets the 'first_try_prepare' variable to
False. So on subsequent recording events RecordTimerEntry.activate() can't
switch to the required channel.
ScanSetup: Add predefined transponders

Thanks Huevos
ChannelSelection: Add option to remove and rename markers

As selecting markers is not available via the normal bouquets lists you
should enable the bouquet edit mode first. Then the new options remove and
rename are available
ChannelSelection: remove a not required mutableList.flushChanges()
ScanSetup: cosmetics by removing space before double quote
Merge remote-tracking branch 'pli/master'.