Added an alternative way of setting the colon-space option

Right now the `colon-space` can only add exactly one space before and/or after the colon and there is no way to remove the whitespace at all.

This PR adds an ability to use strings like `" "`, `"\n"`, `"     "`, `":  "`, `"  :   "` etc. so you could either set the space after colon to be any number of whitespaces, or you could set both the before and after by using a colon symbol inside the option value. And also, by using `":"` value you could remove the whitespace at all.