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!()

Initial commit