Moved User.toString to Utils so it can be used elsewhere

User.toString() was formerly private and would check to see if a
JSONObject was null before we convert it to a String

I moved the funciton to the Utils class and made it public so that we
can construct Submissions with a JSONObject (something that we do over
and over again in User.java)
Overloaded Get function to not take HTTP params
UTC Time is represented by a double
Function to get Saved Submissions
Merge pull request #2 from evinugur/karan

Moved User.toString to Utils so it can be used elsewhere