Currently plugin searching still works in two stages, first it searches
for all plugin broadcast receivers and then waits for all the answers
to complete the plugin map. If any of plugins doesn't answer the call
this means all of them won't be shown and that's not very user-friendly.
The change simplifies plugin search to just package scan for specific
broadcast receivers. Android provides package name and app info for it.
We don't need any other info from plugins, so we don't need to wait for
broadcast roadtrip.
Further improvements:
* introduce meta-data and uses-feature tags in
plugin manifests and get rid of broadcast receiver completely.
* Implement view in settings activity with list of installed plugins
50d8d43b54