Use "System Small" fonts in BundlePreference table

The default size of the preference pane limits the amount of the description for the bundles we can show to a couple of words in most cases. By using a small font in the table view we can show more of the bundle description and it also minimizes the amount of resizing of the pane we have to do to see the entire description string.
Save VariablesPreferences.xib with Xcode 5.1.1 (5B1008)
Use "System Small" font in VariablesPreference table

Since variable strings can be very long and we reduced the text size in the bundle table, let's use a small font sizes here to be consistent.
Add search field to Bundle preference pane