POC: switch to extender approach for starting/stopping plugins, reduce webapp to thin bootstrap layer
Set TCCL so javax.mail can find its implementation
Use global index for the main extender bundle
Add secondary index in nexus-extender for embedded components that don't already have an index (namely sisu-resource-scanner, but there may be others)
Can go back to local index now
Enable indexed-scanning of plugins/bundles
Use OSGi services to communicate between bootstrap and extender