This eases the usage of port forwarder as the caller code doesn't need
to store previous used port and now can rely on port forwarder doing
all the hard work.
PR #17967.
Normalize Web API method names.
Allow to use alternative Web UI.
Switch Web API version to standard form (i.e. "2.0").
Improve Web UI translation code.
Retranslate changed files.
Add Web API for RSS subsystem.