Fix for integer mapper where property value is an empty string. Fix for ...

Hi Mike,

Could I please get these couple of fixes merged please?

The integer mapper was crashing if the property value was an empty string, so I have put some defensive code in for that case. Also,the Nullable mapper had its logic the wrong way around.

I've changed the TemplatePage and ViewPage classes to use the UmbracoService as this gets content from the cache where possible, which is what we want when rendering content on the front-end.

Thanks,
Dan.