Backport Flightgear server from private tx branch, collapse commits.

* Added Flightgear multiplayer output interface to uhd_modes.py. This allows flight with live traffic in fgfs.
* Quaternion library borrowed from PyPi and modified to generate angle/axis representation and construct rotation quat from lat/lon to ECEF.
* Miscellaneous enhancements and cleanup to fix timestamps, add aircraft type field (seems to be unused anyway), turnrate info

include/air_modes_types.h

@@ -31,7 +31,7 @@ struct modes_packet {
 //	unsigned char confidence[14]; //112 bits of boolean high/low confidence data for each bit
 	unsigned char lowconfbits[24]; //positions of low confidence bits within the packet
 
-	unsigned long parity;
+	unsigned long crc;
 	unsigned int numlowconf;
 	framer_packet_type type; //what length packet are we
 	unsigned int message_type;

include/modes_crc.h

@@ -20,10 +20,10 @@
 # 
 */
 
-#ifndef INCLUDED_MODES_PARITY_H
-#define INCLUDED_MODES_PARITY_H
-extern const unsigned int modes_parity_table[112];
-int modes_check_parity(unsigned char data[], int length);
+#ifndef INCLUDED_MODES_CRC_H
+#define INCLUDED_MODES_CRC_H
+extern const unsigned int modes_crc_table[112];
+int modes_check_crc(unsigned char data[], int length);
 bruteResultTypeDef modes_ec_brute(modes_packet &err_packet);
 unsigned next_set_of_n_elements(unsigned x);