OWMiniAtAndroid: Remove unused variables, convert instance variables to local variables when it can be done, remove an unused import, and change from StringBuffer to StringBuilder.
OWMiniAtAndroid: Remove most of deprecated methods and constants, and use updated methods and constants.

Despite the labeling in the preferences, the main activity screen is kept on at full brightness, and the setting applies everywhere else.
OWMiniAtAndroid: Encapsulate ScanService's scanData and ScanData's lock, and provide getters for both.

This is the start of encapsulating non-private variables.