Fix: disable kernel event based on name and event type

The -a argument is interpreted as a zero-length event name
instead of '*' which is actually a valid wildcard event
name by itself. This simplifies how a disable command is
handled by the session daemon.

The event type can now be passed as argument and is a
new criteria while disabling kernel events. The default
is to disable for all event types.

UST and agent domain do not yet support disabling by event
type.

e.g:
	# Only disable kernel event of type tracepoint.
	lttng disable -a -k --tracepoint

	# Only disable the event with name '*' and type syscall.
	lttng disable -k '*' --syscall

	# Disable all kernel event of all type.
	lttng disable -a -k

Fixes #925

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>