Move dependency to sentry-stub in jetty plugin
Remove redundant configuration
Check compatibility with 1.6 with animal sniffer
Do not double build (animal sniffer already checks that)
Indentation
Force charset to UTF-8

UTF-8 has to be provided by every implementations of the JVM, so
there is no reason to rely on that all the time.
Update README.md
Split README and INSTALL
Make the JNDI name a constant