Allow timeinput without ':'

[Jonas-Marty]

Block times must be entered by explicitly enter 7:00 or 07:00.

I'd like to enter times similar to https://sbb.ch, there I can enter different formats that get auto formatted:
700 = 7:00
7.00 = 7:00
0700 = 07:00
7 = 7:00
07 : 7:00

Time input may depend on culture - this feature is therefore possibly specific to (swiss-) german input culture.
As I guess Ecamp is currently only used in Switzerland this feature can be limited to be working with this culture and ignored for others.