Android Scanner Compat Library Versions Save

New features:

• #33 - Scanning with PendingIntent supported (and emulated on older platforms using a background service).
• #44 - SCAN_MODE_OPPORTUNISTIC falls back to SCAN_MODE_LOW_POWER on Lollipop and to power save settings on older devices.

Bugs fixed:

• #39 - fixed infinite scanning with #40.

Improvements:

• #32, #34, #36 - Fixed race conditions, supported worker thread, simplified code

Bugs fixed:

• #20

• Support for Android Oreo added

• JUnit tests added