Add ImageProcessor cached files and nuget package updates

This reverts commit 5b168d4300.

Amends #1131 - fixes Umbraco template to compensate for the change in the
VisualStudio template which would lead to issues if the two were used together.
These rules were originally added by @bbodenmiller in #1013

From the discussion on #1013:

Since the rule in VS is packages/*, the fact that it contains a slash means
that it is anchored to the top level. That is, is will only apply to
a directory called packages at the top level, and not to any at deeper
directories like App_Data. So these rules at the bottom of your changes
actually aren't necessary after all. I just confirmed this with a quick test.