Derive `aurel-info-mode' from `special-mode'
Inherit aurel-info map from button/special maps
Separate filter map from `aurel-list-mode-map'

Also clean up some bindings.
Add 2 new parameters returned by AUR server

The new "PackageBase"/"PackageBaseID" parameters seem to coincide with
the old "Name"/"ID" ones, so just add those to `aurel-aur-param-alist'
to get rid of the warning messages.