Target prefetches for common grouped comments queries.

Just prefetch_all for everything else.
prefetch_all for 'all' comments view (/forum/all)
removed tagline per community discussion

ref #145
Merge pull request #244 from duckduckgo/zac/removeplaygroundref

removed tagline per community discussion
Merge pull request #235 from duckduckgo/forums-prefetch

Target prefetches for common grouped comments queries.