Run integration tests against a PolyScopeX URSim in CI

Now that we have the External Control URCapX released, we should add
that to our setup instructions.

Downloads the latest version of
https://github.com/UniversalRobots/Universal_Robots_ExternalControl_URCap/releases
or
https://github.com/UniversalRobots/Universal_Robots_ExternalControl_URCapX/releases
and installs that on the URSim container while starting.

…ad URCap (#308)

The API is rate-restricted on an IP address level. And with IPv4 that IP
address is potentially shared between many users of the same ISP.

This PR uses the release web pages to find the latest release.
Basically, it uses the link to the latest release which will be
forwarded by GitHub to a web page using the latest version. Thus, we can
get the latest tag from the redirected URL and use that to build a valid
download link for the latest release.

This should fully validate input argument parsing.

We have been a bit inconsistent in the past when it comes to naming
public members.

While the changes in 71bab65 and
42cf147 would probably not impact many
people, the changes from bef94bb would
be more impactful.

Potentially there would be many more changes in the message structures
for the primary and RTDE interfaces which I have disabled for now.

…303)

This PR aims at supporting to send MoveP and MoveC commands to the robot
directly through the TrajectoryPointInterface and the
InstructionExecutor.