Merge pull request #93 from moon-bear/coding_style

Unify coding style
Import the MAVLink
Makefile: add the mavlink files
Create task "ground_station_task"
Modify the implementation of the function "send_package"
Add file mavlink_types.h into the "mavlink" directory
Enable the Ground Station mode
Add some simple test of the MavLink
Send the attudude data through mavlink
This value shoud be radians
Rename "configSTATUS_SHELL" to "configDEVELOP_SHELL"
Add the compiler macro of the Shell
Add the Ack Message test of the MavLink
Rename the "ground_station_task" to "ground_station_send_task"
Create the task "ground_station_receive_task"
Create local mavlink function "get_mavlink_message"
Create the task handler of the "ground_station_send_task"
Fix the wrong index of the buffer array
Create the global buffer array variable to receive the mavlink data
Using the Mavlink API to get the message from the ground station