Revert "Remove redundant Umbraco exceptions to VS rules"

This reverts commit 5b168d43.

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

Umbraco.gitignore

@@ -10,3 +10,8 @@ Cached/
 
 # Ignore Umbraco content cache file
 **/App_Data/umbraco.config
+
+# Don't ignore Umbraco packages (VisualStudio.gitignore mistakes this for a NuGet packages folder)
+# Make sure to include details from VisualStudio.gitignore BEFORE this
+!**/App_Data/[Pp]ackages/
+!**/[Uu]mbraco/developer/[Pp]ackages