use two step conversion; allow more customization

[mojavelinux]

• load document and convert in discrete steps
• set page title using the Document#doctitle method
• only source highlight if source-highlighter is hightlightjs
• only source highlight blocks with an explicit language declared
• allow showtitle, source-highlighter and sectanchors to be disabled
• explicitly set safe mode (set to default value)
• add hljs to source blocks with no language to fix style problem

[nawroth]

Really nice way to grab the doctitle :-)

[mojavelinux]

:+1:

Indeed, that came with some improvements in 1.5.0.