Convert "cylc dbviewer" to a file chooser for gcylc.
Removed unnecessary command-line passphrase option.

suite-switchable gui would not be able to attach to suites with
passphrase in a non-standard location.
Took tmpdir config inside gcylc.
Start-up views via gcylc.rc; allow start-up with no suite specified.
Added "open new suite" to File menu.
Handle failed dynamic host selection.

run_get_stdout wasn't returning all useful information; and in task.py
returning immediately after failed host selection resulted in an
exception in the job queue thread later on.
Restored right-click menu for db operations.
Removed obsolete dbviewer gui (TODO: update docs).
Updated documentation for combined GUIs.
Removed obsolete sections from the suite.rc reference.
Renamed former db_viewer module appropriately.
Disabled gcylc Quick Guide pending update.
Updated gcylc documentation menu actions.
Fixed a new indentation error.
Document connecting to remote suites with gcylc at start-up.
Removed unnecessary "0" range() args.
Better gcylc File Open menu names.

"Switch To Another Suite" suggests using the existing view window.
Fix gcylc updater thread bork on starting with a running suite.
Removed a stray newline character.
Double-click in db chooser to select suite.