Adding methods for common sensor_fusion flow

Adding methods for common sensor_fusion flow

- Adding new methods for a common orientation computation flow
irrespective of the sensors used in the inputs
- Changing sensor inputs to pointers for checking if inputs are
enabled.
- Tested on rotation_matrix functionality which is not used in any
virtual sensor and using standalone test code.

Change-Id: I763305f06346db2cce87c61e870c0a43f0d1e0e0