message_iter_write!: Support writing Dict
dbus_spec: Fix Ref/Variant
dbus_type: Fix DBUS_TYPE_BYTE
examples: Add GeoClue2 example
message: Support Variant read/write
Add ObjectPath support

Enable thread-safe mode at init
Add notify-send example
Un-export connect and request_name!
bus: Allow selecting bus kind in connect()
Add more APIs

Split out APIs by category
Add more connection APIs
Add more bus APIs
Add message APIs
Add pending call APIs
Add working connect() and request_name!()