Adding search functionality to Hub

[raykendo]

Hello,

This PR is to possibly address #5, where you wanted to search for hub items. I wasn't sure how to search for a Hub by itself, since those aren't necessarily exposed as items in an org. What this does is search for hub items like Initiatives, Sites, Pages, etc. and creates a list of those items. I attempted to follow the patterns you set in other searches.

If this wasn't the functionality you were looking for, feel free to dismiss this one.

EDIT: Didn't realize it, but this pull request also includes managing the layout of a Hub Page in sites.py. Was going to add that in a separate PR, but oh well.