Search api and single page loading, load more button

[mblackstock]

• implement simple query api as documented on wiki that corresponds to UI features
• only load a single page at a time of nodes & flows for faster page load
• use ajax in front page templates/_gistitems.html to load things with AJAX load more button, update URL, support history
• rework query code in lib/view.js to support needed queries, counts
• rework routes/index.js to load page, then load html and counts with AJAX call.