Revert "Removed code that resets the access time if there are less than minTabs open"

This reverts commit 581dbbc72bf0e57422e83ca9275acb5ef0e603a7.

Conflicts:
	background.js
Moved functions around so the generic functions are at the top.
Removed high end value checks on minTabs and minutesInactive.  Flipped default for clearing corral on quit.

TW will behave perfectly well with values above those thresholds, so there's no reason to set those limits.
Init function is now much simpler (but does the same thing). Copying to cache is now taken care of by an event.

Upgraded underscore.js to latest version to support some of these changes.
Implemented new enable sync feature backend.

New feature allows user to disable syncing of settings between computers, in case they want one computer to have different settings than all others.
Added frontend for enableSync feature.
Added basic logic for a close button on each item in the corral.
Close button now floats to the right.
Added images for the close button.
Changed terminology from close to clear.
Added logic to have the clear button change when it is hovered over and fade in and out when the row is hovered over.
Fixed column widths and code style.  Clear buttons now working properly.
Modified clear button images.
Closed time is reverted to being stored as a long for backwards compatibility.  Fixed misspelling on saved tabs.
Fixed context menu so that adding a tab to the corral works.
Saved tabs are now re-saved when a single tab is removed.
Closed count is updated on init.
Merge branch 'refs/heads/settings-refactor' into new-master
Merge branch 'refs/heads/clear-by-item' into new-master
Merge branch 'refs/heads/tab-manager-refactor' into new-master

Conflicts:
	js/settings.js
	js/tabmanager.js
	popup.js