Doc engine improvements.

Bug Fixes:

* Fixed missing variable replacements.
* Removed hard-coded host names from configuration file paths.

Documentation Features:

* Allow command-line length to be configured using cmd-line-len param.
* Added compact param to allow CSS to be embedded in HTML file.
* Added pretty param to produce HTML with proper indenting.
* Only generate HTML menu when required and don't require index page.
* Assign numbers to sections by default.
* VM mount points are now optional.

test/lib/pgBackRestTest/Common/HostTest.pm

@@ -49,7 +49,7 @@ sub new
             {name => 'strImage', trace => true},
             {name => 'strUser', trace => true},
             {name => 'strOS', trace => true},
-            {name => 'stryMount', trace => true}
+            {name => 'stryMount', required => false, trace => true}
         );
 
     executeTest("docker rm -f $self->{strContainer}", {bSuppressError => true});