Bug 1061126: Add AVRCP_UID_SIZE to Bluetooth, r=shuang

This constant AVRCP_UID_SIZE replaces the corresponding Bluedroid
constant BTRC_UID_SIZE.
Bug 1061126: Fix constants in Bluedroid HFP manager, r=shuang

This patch replaces the remaining Bluedroid constants from Bluedroid's
|BluetoothHfpManager| with Gecko constants.
Bug 1061126: Make Bluetooth AVRCP interface generally available, r=shuang

The methods of |BluetoothAVRCPInterface| are now always available. On
Android versions before 18, which don't support AVRCP, they always
fail with STATUS_UNSUPPORTED.
Bug 1061126: Cleanup ANDROID_VERSION from BluetoothA2DPManager, r=shuang

All interfaces for Bluetooth profiles are now always available, so we
don't have to check for specific versions of Bluedroid. Instead, we
try to call the methods, and check their results.