initial upgrade for vs2012
Fixed a small issue where the Theme Manager could not open a file that was saved to %TEMP% (or, in reality: saved as Read-Only).

The fix involves simplying passing 'FileAccess.Read' in the
Package.Open method. This without an explicit FileAccess mode, the
underlying File.Open will default to 'FileShare.None' which will throw
an exception (UnauthorizedAccessException).