Add an abstract class for IMU, just framework.
Add IMU IG500N support, just framework.

Signed-off-by: Eric Dong <eric.dongxx@gmail.com>
Add source build directory to include subfolders such as common,
navigation.
Add another abstract class CTaskThread to handle multiple task threads
architecture.

Signed-off-by: Eric Dong <eric.dongxx@gmail.com>
Add common functions such as byte element operation.
Implement the abstract class of CTaskThread.
Implement the child class CIMUIG500.

Signed-off-by: Eric Dong <eric.dongxx@gmail.com>