OE2.5 Merlin4 For DM 520-525 HD-04.02.2018

Merlin OE-2.5 revision 747:
- ChannelSelection settings:
-- always show DVB-icon option
- PiconLoader / PiconMapper:
-- adjust some logic to PiconResolver (this fixes issues with new Partnerbox service reference)
- PiconMapper:
-- really update existing entry instead of re-adding it
- Replace DreamCC with SysCC