Points: make URL check more helpful

When entering an address in the way you're used from business cards, advertisement, browsers etc, Locus says Wrong item 'URL'

and blocks saving of the point.

For users, this is not easy to understand in the sense that it is not that much helpful to solve the issue: Is no URL item allowrd for that point type? Is the given URL wrong for that point or field type? If just the formatting is wrong, what formatting is accepted? etc.

Please either

• For URLs without schema, ask "Add http:// in front? yes/no" which can be assumed to be the usual schema. If yes, prefix http:// and retry URL check. If no, show current validation result message but reword to Wrong URL format, expecting scheme:// prefix or 'http://www.domain.tld' (i.e. list the restrictions the implemented checks for).
• or accept any URL without scheme and with different hostname than "www" (especially no hostname at all) and also without TLD, so e.g. germany.example.com and example.com and myRouter:8080/foo are allowed