Retrieve IDBObjectStore by objectStore name rather than database name

[ankushnarula]

When retrieving an IDBObjectStore, the IDBDatabase.transaction method should take the name/names of one or more objectStores rather than the name of the parent database as the first parameter.

Reference: https://developer.mozilla.org/en-US/docs/Web/API/IDBDatabase.transaction#Parameters and here: https://msdn.microsoft.com/en-us/library/ie/hh772509(v=vs.85).aspx

NOTE: The Mozilla example code makes this confusing since it uses the same name ("todoList") for both the database and for the objectStore