Working draft of the category hiding feature. No schemamigration yet in this commit so if you checkout this, make your own schemamigration.
Merge branch 'master' into category_filter
CAUTION: Includes schemamigration! It is a simple one so no worries.
Added the category filtering feature for the instance view. Users may now toggle visibility of categories in their schedule from the form that is displayed through the "Filter Categories" button. The collapse div for the form is by default open as requested but will be closed by default later.
Merge pull request #70 from Rubinous/category_filter

Category filter