Allow configuration of caldav in GUI

[Eeems]

It would be nice to be able to add the ability to set the URL, username, and password in the GUI instead of having to edit the configuration file on disk.

[tenJirka]

Agree, I'm considering if it won't be better wait until this issue will be solved, because I would like to add keyboard with support for Czech as well (that's problem when some letters will not be able to display) which will be needed for edit functions which I would like to add.
There are few symbols missing in Simple keyboard like +, #, _ so I will probably design own keyboard anyway.

To sum it up,I plan to do implement it, but not sure which way chose.