Add Denon communication protocol

In order to control Denon/Marantz AVR, add Denon communication protocol:

Basic functionality described in https://github.com/mkulesh/onpc/blob/master/doc/Denon/FY21_AVR_DENON_PROTOCOL_V02_04062020.xlsx
Processing of Denon Receiver information message (e.g) https://github.com/mkulesh/onpc/blob/master/doc/Denon/ReceiverInformation/DRA-800H.xml: List of zones, list of controls, input selectors, tone control
Receiver discovery based on HEOS SSDP requests
Playback and media control using HEOS protocol
Hide Onkyo-specific GUI elements (Tabs RI and SHORTCUTS), some parameters in tab DEVICE
Update App description

Known bugs for Lite version:

No cover images for Android 4.2, 4.4 (for some sources). Starting from Android 5.0, all cover images are shown. Onkyo cover images are shown on all Android versions.
Playback buttons for zone 2 has no effect (fixed in premium version with bc8f5d8b)

Known bugs for Premium version:

Scroll at back does not work for Denon when more than 100 entries (due to several item packets)
No UDP search results for Denon on Windows

mkulesh / onpc