Scan diagnostics

[navaronbracke]

Users have indicated that sometimes their results differ from person to person when scanning for devices.

We should allow them to enable diagnostics to identify the problem.

TODO:

• add a toggle on the settings page to enable diagnostics
• add a help button next to it that explains what it does
• add a ScanDiagnosticsLogger class implementation
  • the class keeps track of a StringBuffer for the contents of the output
  • receives data from the scanning delegate at appropriate times
  • writes the output to a file when the scan ends
• write events for devices that are intercepted by the Bluetooth Adapter, but are excluded from the search results
• write timestamps for each event
• write the reason why it is excluded?