Hint active/inactive state of mscolab server.

[Shivashis Padhi]

Right now, the mscolab triggers errors if server isn’t active. Hint the user if mscolab is active by pinging it. Take url as input from user.

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[Reimar Bauer]

Merged in plant99/mss/i460 (pull request #714)

Fixes#460 Url input for mscolab server, includes tests

→ <<cset b1626fabcd25>>