error forgiveness for server address input

[jancborchardt]

Currently you need to put in an exact server address, including the protocol. Otherwise you get an error: »Please add a server url that starts with http.«

Instead, it should be possible to just put in an address such as example.com/owncloud – it should automatically be checked for https connection first, and if that doesn’t work for http. Only if that doesn’t work, give an error which says to double check the server address.