I for some time miss the command copr edit-chroot, and I didn't have
time to implement it properly. And now, when thinking about #1334, I came
to an idea...

What if we removed all the options there on the web page, and only added
one textbox area instead which would provide "additional mock
configuration"? Copr would just concatenate the default config with the
one provided there. The mock configuration is order independent nowadays,
so it shouldn't make any practical difference.

That would give much much more powerful tool to any users as they could
experiment with any feature mock provides without forcing us to implement
additional knobs.

And it would simplify our life because there would be basically one field
in the form and -- WRT /bin/copr and API -- the command wouldn't have to
have any options (only copr edit-chroot CHROOTNAME FILENAME).

The negative of this proposal is that we would loose the form with all the
special-cased options. If this was the problem for anyone, we could
either
- keep both variants (something like expert/normal mode)
- keep the form JS only, and let it pre-fill the mock config snippet

Ideas?