Add:osd/core:

Add:osd/core:
- added the possibility to set attributes of OSDs runtime
- added navit command for setting attribute of a named osd
- added the possibility to set src attribute (background image) of osd buttons runtime
- created "command interface" osd type to be able to access command system accessible data (for example route_status) and display it either as text or image (see Ticket #815 for details)

git-svn-id: https://navit.svn.sourceforge.net/svnroot/navit/trunk@4432 ffa7fe5e-494d-0410-b361-a75ebd5db220