Grouping multiple event streams to use single netty bootstrap, thread pools and etc.

[andll]

EventSourceClient introduced, it allows to utilize single netty bootstrap for multiple event streams, granting singnificant performance on multiple event-stream connections.

Before, every EventStream used its own netty bootstrap, which means that application will use 3*event_stream_count threads.

Event stream content-type detection fixed, now it accepts event streams with addition data in content type

maven-gpg-plugin now runs in disabled by default profile sign