Add a new option to the livetable macro to output only HTML content, without syntax wrappers

Currently, the livetable macro assumes it is only called from wiki pages that are written using wiki syntax (1.0 or 2.x). Because of this, it wraps the html output of the #livetable macro call with

{{html}}{{/html}}

for syntax 2.0 and

{pre}{/pre}

for syntax 1.0.

We have recently agreed that the livetable macro is a core feature and it should be used inside filesystem template whenever needed, given that it implements its own template-based data source, other than the document-based data source (XWiki.LivetableResults) that might not be present in the environment.

To accommodate this, we need to allow templates to easily use the livetable macro without getting the useless wiki syntax wrapping the macro's output. For this, an extra outputOnlyHtml option would be useful in the livetable macro to specify that the wiki syntax wrapping should not be added and the macro should output only the raw html.