major change in PMS handling

PlexAPI
- g_PMS to store server properties per aTV
- declare, search, access functions (class-like?)
- discover: checks GDM + MyPlex
- intermediate XMLFromMultiplePMS: add PMS address, similar to aTV
WebServer
- removed: try to discover
XML_converter
- discover whn aTV app starts - ie PlexConnect.xml is requested
- handle PMS() data in URL, IMAGEURL
- rewritten PMDCOUNT, PMSNAME
Settings
- removed "toggle PMS"

Known issue…
when cancelling out/at the end of video replay, the PrePlayScreen is
not found ->PMS unknown.