Improve configuration explanation for users

Expended the input documentation with the possibilities that the current implementation already has.
This is very useful for first time users and users that don't look in the underlying code.
Making these configuration possibilities obvious, can attract more users in selecting this product.

Config.groovy

@@ -30,9 +30,14 @@ confluence = [:]
 // - 'file': absolute or relative path to the asciidoc generated html file to be exported
 // - 'url': absolute URL to an asciidoc generated html file to be exported
 // - 'ancestorId' (optional): the id of the parent page in Confluence; leave this empty
-// 							  if a new parent shall be created in the space
+//                            if a new parent shall be created in the space
 // - 'preambleTitle' (optional): the title of the page containing the preamble (everything
-//                               before the first second level heading). Default is 'arc42'
+//                            before the first second level heading). Default is 'arc42'
+// - 'spaceKey' (optional): page specific variable for the key of the confluence space to write to
+// - 'createSubpages' (optional): page specific variable to determine whether ".sect2" sections shall be split from the current page into subpages
+// - 'pagePrefix' (optional): page specific variable, the pagePrefix will be a prefix for the page title and it's sub-pages
+//                            use this if you only have access to one confluence space but need to store several
+//                            pages with the same title - a different pagePrefix will make them unique
 //
 // only 'file' or 'url' is allowed. If both are given, 'url' is ignored
 confluence.with {
@@ -68,4 +73,4 @@ confluence.with {
     // extraPageContent = '<ac:structured-macro ac:name="warning"><ac:parameter ac:name="title" /><ac:rich-text-body>This is a generated page, do not edit!</ac:rich-text-body></ac:structured-macro>
     extraPageContent = ''
 }
-//end::confluenceConfig[]
+//end::confluenceConfig[]