Adding more encoding for VNC server

Currently only limited encoding types are supported:
https://doc.qt.io/QtVNCServer/index.html#encodings

There are many others out there and some customers are asking for them:
https://en.wikipedia.org/wiki/RFB_protocol#Encoding_types

Particularly, people are asking for:
Tight (0x00000007)
Tight PNG (0xFFFFFF74)
Compress level (0xFFFFFF00–0xFFFFFF09)
Quality level (0xFFFFFFE0–0xFFFFFFE9)