cylc test-battery: fix get-global-config for site.rc hosts.

This fixes the get-global-config test when more than one
site.rc host is specified. This is due to the use login
shell line appearing once per host, not just once.

The sed change takes the first occurrence of use login
shell following a line that looks like [[localhost]].
Strip file lines after all processing, not during inlining.
Move file inlining into lib/parsec.
Cleaner section heading parsing.
parsec.validate: ignore space in list+space+jinja2
Removed unnecessary line strip.
Corrected erroneous use of unset in the test battery.
Line continuation markers must be final character.
Adjusted tests for new default titles and descriptions.
New command to check task host cylc versions.
cylc hold: fix documentation on CLI syntax
Merge pull request #856 from matthewrmshin/fix-cylc-hold-doc

cylc hold: fix documentation on CLI syntax
Detect mismatched quotes in %include lines.
Allow whitespace before and after comma in section heading lists.
Test validation with a lot of arbitrary whitespace added.
Merge pull request #852 from benfitzpatrick/cylc-test-battery.fix-hosts-get-global-config

cylc test-battery: fix get-global-config for site.rc hosts.
cylc gui: add toolbar item text.

This adds proper text for toolbar items that is
shown when users have particular Gnome configuration.
cylc gui, cylc graph: rename 'landscape' mode.

This renames the 'landscape' graphing orientation mode to
more understandable 'left-to-right' titles.
Added omitted test suite include-file.
Merge pull request #857 from benfitzpatrick/cylc-gui.toolbar-text

cylc graph, cylc gui: add toolbar text, rename 'landscape' mode