[BETA] v0.8b - Ready for testing

Changes & Fixes
* Added NEW FEATURE: Open/Close position, which links to the Contact Sensor capability. Using code kindly shared by GitHub user @_Oltman, custom open and close positions can be stored by pressing the _Set Open_ and _Set Closed_ UI tile buttons while the sensor is in your desired open & closed positions. Once set, the DTH will generate `contact - open` and `contact - closed` events when the sensor is in nearly the same positions. 
* Changed the method to initially set and display hardware Sensitivity level when the sensor is paired (If sensor is already installed, open preferences and press "save" to set up the Sensitivity level UI button.
* Improved the code that cycles through the 3 levels when Sensitivity level UI button is pushed
* Changed "Vibration Level" to more representative name "Last Activity Level"
* Moved code to reset to Stationary status from `updated()` to `configure()` so that that status isn't reset to _Stationary_ when preference settings are saved, instead only resetting it when the sensor is first paired
* Added code to initialize _Last Activity Level_ and _Last Angle Change_ UI tiles to display "--" if no reported values have been received yet.
* Various code cleanup and formatting fixes