Issue #196 - Fixes QDateTimeElement multiple initializeRoot calls bug.

QDateTimeElement's `initWithTitle:date:` initialisation method calls `[self init]`, which calls `[self initializeRoot]`, but `initWithTitle` calls it again after setting the title and date.

To fix it, I initially cleared the sections array in initializeRoot, but this is kind of unnecessary. The elements just need to be updated since they are already created and initialised during init. So I added an updateElements method, which grabs the QDateTimeInlineElements by key and updates their dateValue to the correct value.

(Addresses issue #196).