Migration cleanup and improvements.

[IMPROVED]  Migration code cleanup.
[FIXED]     When local store migration fails, fall back to opening the old local store if possible.
[FIXED]     Better migration of cloud preferences.
[FIXED]     Better checking of when to perform cloud store migration.
[FIXED]     Always migrate the local store, even when the cloud store is enabled.
[UPDATED]   Removed the loading indicator in favor of a loading overlay.
[UPDATED]   Sorted the file references lexicographically.
Temporary moc fix, setup & new guide.

[FIXED]     Pass along temporary mocs, they appear to be stored __weak in the object and we can't rely on them not being nil.
[ADDED]     Setup flow for initially setting the iCloud preference.
[ADDED]     New guide.
[IMPROVED]  Hierarchy and flow of unlock -> main.
More fixes of temporary moc accesses.
Setup and guide.

[FIXED]     Setup wasn't showing up on app load.
[FIXED]     More temporary moc fixes and main thread fixes.
[IMPROVED]  Guide now plays an introduction animation.
[FIXED]     Setup iCloud switch is now functional.
Search & AllSites improvements, sort by recency, rememberLogin setup.

[UPDATED]   Simplified AllSites VC in IB (removed the unused navVC).
[UPDATED]   Outdated sites are now shown in the AllSites VC.
[ADDED]     An update-all-sites button when showing outdated sites in the AllSites VC.
[REMOVED]   Search scopes.
[ADDED]     Sorting elements by recency and usage count now.
[FIXED]     Initial positioning of help container.
[ADDED]     Setup VC for rememberLogin.