add API BLEDevice::shutdown() to purge the BLE stack of GATT and GAP state.
init() should be called before restoring state.

fixes #15.
Release 0.2.7
=============

API enhancements to support purging of GATT/GAP state.

Enhancements
~~~~~~~~~~~~

* Add API BLEDevice::shutdown() to purge the BLE stack of GATT and GAP state.
  BLEDevice::init() should be called before restoring state.

* Minor update to API for GattCharacterisitc: add getValueHandle() as a
  shortcut for getValueAttribute().getHandle().

Bugfixes
~~~~~~~~

Compatibility
~~~~~~~~~~~~~

This release is backward compatible with 0.2.4.