Bug fixes after new backend updates

[Jchen20-1]

Please do work for this task in a branch called issue-138.

Fix:

• [x] committing to events returns error (most likely just need to update the meteor methods being used to update users and events collection)
• [x] User Profile page shows blank for the user's image, most likely a typo somewhere since the homepage has the image working
• [x] dashboard dropdown and page doesn't show the list of organizations even after confirming that the organization was created and added to the Organization collection.
• [x] adding events requires a new category field, where it has the mainCategory and subCategory, need to create new fields in the form when creating events.

[jianleliu]

activityCategories

• mainCategory
• subCategory

will now be optional and default to "Other".