Altering how the jetpack-tools-to-include works to make it do something useful.

Currently this filter does a whole lot of nothing, though it was designed by @tmoorewp with good
intent. Updating the filter so that it actually does what is expected of it.

This first commit includes the initial POC that it will indeed work with the Social Links.
Moved holiday-snow.php into the jetpack-tools-to-include filter

This will still automagically run holiday-snow.php by default, but also makes it a bit easier to
turn off if the site admin feels it is frivolous :)
Add Random Redirect to jetpack-tools-to-include filter
Update new Social Links loader to correspond with the original init hook priority
Add featured content, infinite scroll, and custom post types to jetpack-tools-to-include filter
Added theme-tools.php to jetpack-tools-to-include filter
Merge pull request #802 from Automattic/tools-filter

Tools filter