Add more "debug" info to table footer

[podliashanyk]

Already displayed:

• refresh interval
• configured timezone

Add info about following:

• configured Zino server
• Add "Last changed: datetime" to footer #107
• number of events displayed in the table
• version of Howitz
• version of zinolib
• version of Zino
• current sort_by method
• on hover over button close to the sort-button, pop up box with info without having to scroll
• ... more?

[podliashanyk]

Nice-to-have: show this info when hovering over a "Table Info" button in the table toolbar:

[hmpf]

• version of zinolib

Because setuptools this is very clunky so as of now I don't want to support it

• version of Zino

While Zino protocol 1 (tcp) does have a command to ask for version, zinolib.ritz does not make it available (curitz cannot know either). I have hardcoded something to talk about the protocol in use for now.