renamed EASY to POSHOLD and SEATBELT to ALTHOLD

src/drivers/blinkm/blinkm.cpp

src/modules/commander/commander.cpp

...s/commander/commander_tests/state_machine_helper_test.cpp

src/modules/commander/px4_custom_mode.h

src/modules/commander/state_machine_helper.cpp

src/modules/fixedwing_backside/fixedwing.cpp

src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp

src/modules/mavlink/mavlink_messages.cpp

src/modules/mc_pos_control/mc_pos_control_params.c

src/modules/segway/BlockSegwayController.cpp

src/modules/sensors/sensor_params.c

src/modules/sensors/sensors.cpp

src/modules/uORB/topics/manual_control_setpoint.h

src/modules/uORB/topics/rc_channels.h

src/modules/uORB/topics/vehicle_status.h