Let the {% adjust %} template tag take unspecified kwargs

[melinath]

Right now, all the methods we can apply to images take the same kwargs. This really doesn't make any sense.

For example, crop accepts max_width and max_height, but these have the exactly the same effect as width and height. It would make more sense to just not have them. Instead, crop could take kwargs that force an x or y offset instead of letting one be calculated (though I don't know that would be a good idea.)

Meanwhile for fit those kwargs have a different effect, but only if width or height is undefined. Really, it would make more sense to just allow width and height, but specify that one or both dimensions are loose - i.e. whether the image should be expanded to fit that dimension as best as possible or not.

[melinath]

Possible syntaxes:

{% adjust <image> <adjustment> <key>=<value> ... <adjustment> <key>=<value> [as <varname> ] %}

{% adjust <image> [lookup] as <varname> %}
    {% adjustment <name> <key>=<value> ... %}
    ....
{% endadjust %}