Very begining CdrskinProgram and CdrskinWriter

Summary:
It is skeleton of migrating to cdrskin, so it might be full of bugs, I
need to be faimilar with cdrskin command...

1. [UI] add cdrskin to the items of Writing app combo
2. [k3blib] add CdrskinProgram inherited from SimpleExternalProgram (not
including *.cue)
3. [k3blib] add CdrskinWriter (it might not suitable for cdrskin command)

Test plan:
burn , for example ArchLinux, iso

CCMAIL: scdbackup@gmx.net
CCBUG: 137436