Clarify re-connection routine

[b3b]

This issue is to address possible steps to document re-connection routine: see PR #33 by @robgar2001

Possible steps:

• BLE.connectGatt() Java method should close current GATT client before connection to new
• Add an example on using re-connection
• Perhaps, add able.BluetoothDispatcher.reconnect_gatt() method as a shorthand for "re-connect to a remote device after the connection has been dropped"