A set of additions related to allow the use of SID and STAR procedures.

A set of additions related to allow the use of SID and STAR procedures.
The current code still has some rough edges, in particular memory still
needs to be deallocated where possible, and the actual use of the code
needs more testing. This code has been running without noticable problems,
so I think it's ready for some wider exposure. Detailed changes include:
- Finetuning of the SID/STAR data concept.
- Preloading of all SIDs, from one xml file.
- ATC determines which SID should be used and echoes this over the com1 or
  com2 radio.