tools: Add support for UIDs changed event to AVRCP parser
tools: Fix passing wrong argument to g_dbus_proxy_set_property_basic

g_dbus_proxy_set_property_basic takes a pointer to value not the value
itself like libdbus does.
unit: Add gdbus/client_set_string_property
unit: Add gdbus/client_string_changed
gdbus: Fix not calling property_changed callback

In case a property did not appear by the time proxy_added was called
property_changed has to be called if it appear latter otherwise the
application will be unaware of it.
gatttool: fix parameter type/name from le to psm

The parameter le was changed to psm and its type was modified from
boolean to int, but header was unmodified. That change occurred in commit
0cc24599637ed6666469c68d55f4e42ff722e447.
gattrib: remove glib basic data types usage
gatttool: un-glib-ing
gatt-service: un-glib-ing
GATT: un-glib-ing
att: un-glib-ing
attrib: simplify boolean tests

Remove unnecessary TRUE/FALSE in boolean tests.
attrib: utils un-glib-ing
WIP attrib: removing gboolean
attrib: Avoid passing raw PDU to Exchange MTU callback

By centralizing the PDU parsing and validation internally to GATT API,
the callbacks become simpler.
unit: Add test for gatt_exchange_mtu()

The new unit/test-gatt.c file will contain tests for GATT API
implemented in attrib/gatt.{c,h}.
attrib: Rename gatt_find_info() to gatt_discover_char_desc()

The old name referred to the underlying ATT PDU (Find Information
Request and Find Information Response) and not to the actual GATT
procedure (Discover All Characteristic Descriptors).
WIP