Changes to Update user API

[callzhang]

I realized that I have removed update base preference API. But I didn't know it until now, due to missing alert view in preference view. Currently, all changes to user will be routed via update user API. After careful thinking, I am going to change the API a little bit.

time	route	parameters or payload	notes
Old	PUT /user/:username	user object	Returns user object
New	PUT/user/:username	{property: value} pair of updates	Returns user object