add a GCD class for custom GCD/block code
Open .xibs and 'fix inconsistencies'

No other changes made
Add method to run block on specific queue
ensure the indexIsValid is run on the scanQueue (avoiding locks)
Set QSTask iVars on the main thread

Ensure that KVO notifications are received on the main thread and UIKit can handle changes correctly
give the scanqueue a better debug name
Revert "prevent a crash related to catalog entry dates"
Reverts commit 5985b7f54c82199b4a6af17694a72459c8f2198d.

This is a multi-thread issue, so checking a BOOL at one moment in time won't fix the problem
Merge pull request #1319 from pjrobertson/crashFixes

Scanning/Threading fixes