doc: Update user guides for Trace Compass release

doc: Update user guides for Trace Compass release

- Update LTTng, pcap and gdbtrace user guides so that they don't mention
  Linux Tools
- Change LTTng User Guide to Trace Compass User Guide. For that, it was
  necessary to reorder and reword a few sections.
- Other minor corrections

Change-Id: I5ae0b88f2de1131865399fe2fc55d1d7de795af4
Signed-off-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/41039
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-by: Hudson CI
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>