allowedMimeRegExp enhancement

[al_9x]

Currently (AFAICT) this is a newline separated rx list and the host part is not handled by addressmatcher.

1) newline separation makes a list difficult to enter
2) no addressmatcher, makes host specification, more cumbersome than it needs to be
3) syntax doesn't support multiple mimes per host

For this setting, being rx is not as important as making it easy to enter a list of sites with potentially multiple mimes for each. Ideally this would be exposed in the ui, but if not, the pref would be more friendly/usable were it space separated, to use adressmatcher, to allow multiple mimes per host (and perhaps multiple hosts per mime):

mime1,mime2@.host1.dom1 mime3@.host2.dom2 mime4@* *@.host3.dom3 mime5@.host4.dom4,.host5.dom5