- removed unused imports.
- split up the interface 'SerialConnectionListener':
	- 'SerialConnection' now uses 'SpeedListener and activeListener
- added the 'Closeable'-Interface
- implemented 'Closeable' in 'SerialConnection'
- removed unused imports.
- split up the interface 'SerialConnectionListener':
	- 'SerialConnection' now uses 'SpeedListener' and 'ActiveListener'
- added the 'Closeable'-Interface
- implemented 'Closeable' in 'SerialConnection'