Manage complete "event rules" in the Java agent

Instead of just tracking which event names are enabled in the tracing
session, we can track the complete name/filter/loglevel tuple. This
allows the same event name to be specified multiple times but with
different parameters.

Right now the sessiond does not send the filter string, a new protocol
version will be required to do so. But we can prepare for it in the
meantime.

The agent will continue to use the event names to decide if events
should be sent through JNI or not. However, full rules will be useable
for other purposes, like the upcoming filter notifications.

Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>