read access to `kde-config --path config` only honors first directory in path
When writing to the kde config it may be a valid assumption that the first entry in
kde-config --path config (or kde4-config or kf5-config per my other recent issues) is the only user-writable location, and the lack of ability to make system-wide changes would be more of a feature request, so neither of those are what this issue is about.
In multiple places in xdg-settings and xdg-mime, calls are made to
kde-config (and related tools) and then immediately piped through
cut -d ':' -f 1 to keep only the first directory on the path. When reading from the config, all entries on the path should be checked until one with the relevant section and key is found.