- find_option returns uint8_t *
- Some constants improved.

- No EDNS processing when server's OPT is not set
- Clearing OPT from packet
- Fixed packet unittest (wrong condition)

Conflicts:
	tests/Makefile.am

TODO: unittests

- Removed EDNS params structure.
- Server now stores the OPT RR itself.
- Removed all EDNS manipulation from packet.
- Cleaned up some EDNS-related packet-checking functions.

Removed some questions and replaced with empty functions left for
implementation, see the #warning lines and implement them.

- old tests dropped, will be useful in rdata_t and knot_rdataset_t
  tests.

Conflicts:
	tests/fake_server.h