chore(MainActivity): Code clean up and formatting

Remove dead code like unused imports and do some code formatting.
feat(SensorReader): Make printing header optional

Allows to surpress printing the device info header. Useful the continue the recording
with the same device at a later point in time.
chore(SensorReader): Sort Members and make final if possible
fix(MainActivity): Disable landscape mode

Switching between Landscape and Portrait caused a lot of trouble while streaming
because the Activity Lifecycle has to be implemented carefully since every switch
between Landscape and Portrait creates a new Activity.

Limiting the MainActivity to Portrait allows still to analyze all the tapping patterns while
keeping the Activity Lifecycle simple.
fix(MainActivity): Stop Recording properly OnPause

Stop recording was not working correctly when called from OnPause.
Also fixes a bug where a stopped recording could not be started again from
the user.

Closes https://github.com/psycholold/SensorReader/issues/23
Merge pull request #25 from psycholold/23-fix-onpause

23 fix onpause