todos leftover from #18

[unkcpz]

Since #18 is quite large and contains major changes about tests and CLI, I get it merged first and move todos for separated small PRs:

• If remote binary exist, cannot override install. Hit sftp error (OSError: Failure)
• Think of is it a new problem after eiger updated, only from the same login node can access the server.
• Specifying HQ_SERVER_DIR explicitly, to distinguish multiple server (see Distinguish hq-server folder to have multiple server for different machines share the same home It4innovations/hyperqueue#719)
• Implementing CLI ports to pause and resume the alloc.