Draft GS6.0 Chapter 1 Draft

I've uploaded GS6001 - Introducing_LibreOffice_PF_20170804.odt to the
Authors website:
and updated the wiki accordingly.

In this draft I:
- Added a line or two about the keyboard shortcuts in context menus and
how to disable/enable them. Included a screenshot that may or may not be
necessary, if not, it will be deleted.
- Added a section to the end of the chapter titled "Troubleshooting
LibreOffice in Safe Mode.

Screenshots at the moment are placeholders. After all changes have been
merged into a single document, I think, for consistency, a single person
doing a review/edit of the merged document should contribute the
screenshots so that visual consistency is maintained.