Add snapshot command to lttng UI

Signed-off-by: David Goulet <dgoulet@efficios.com>
Implement snapshot commands in lttng-sessiond

Basic functionalities are implemented in the session daemon so handle
snapshots and send the command to the consumer but note that at this
commit the consumer does not handle snapshot.

Signed-off-by: David Goulet <dgoulet@efficios.com>
Support flight recorder mode for a session

This adds the --no-output option to the lttng UI which will flag a
session to not set an output destination meaning that tracing will be in
overwrite mode in the buffers.

This is also the only way for now to snapshot a session, it's to put it
in no output mode.

Signed-off-by: David Goulet <dgoulet@efficios.com>
Add kernel snapshot support

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>