Fix several visual issues with find result highlighting:
- Reduce width of scrollbar tickmarks to match new, narrower custom-themed
scrollbars (should also look better on Mac, where the tickmarks were already
too wide)
- Fix bug where showing/hiding a bottom panel didn't update the positioning
of scrollbar tickmarks
- Results that span multiple tokens showed little orange dots in the text
highlight between tokens (due to repeated corner rounding). There are still
faint lines between tokens (due to box-shadow), but they're much fainter.
maintain folder expanded state when last child is deleted
Use jstree open_node in corner case #6474 where renaming the only file in a directory caused duplicate tree nodes to appear
simplify state validation for directories
find in files stays in a single line
Changes QuickView over to the new preferences system
Merge pull request #6495 from adobe/jasonsanjose/issue-6483

Maintain folder expanded state when last child is deleted
Merge pull request #6522 from adobe/jasonsanjose/issue-6474

Prevent duplicate tree nodes when renaming the only file in a directory
Merge pull request #6478 from adobe/pflynn/find-highlighting-tweaks

Fix several visual issues with find result highlighting:
Merge pull request #6534 from adobe/dangoor/quickview-pref

Changes QuickView over to the new preferences system
Merge pull request #6529 from ishanatmuz/followupFor#6348

find in files stays in a single line
comment out use of defaultExtension pref to avoid problems with ScopeManager
Merge remote-tracking branch 'origin/master' into bchin/disable-defaultExtension-pref
Fix bug #6542 (Exception thrown on save if file not visible in project
tree) - move initialization of wasOpen after the check that early-exists
when $directoryNode is null.
Merge pull request #6545 from adobe/pflynn/fix-tree-npe

Fix bug #6542 (Exception thrown on save if file not visible in project tree)
Merge pull request #6543 from adobe/bchin/disable-defaultExtension-pref

disable defaultExtension pref, for issue #6539
Fix for #6541 that leaves preferences in place after conversion.

When you switch to Brackets 36, preferences will be converted automatically.
If you switch back to an earlier Brackets, your old preferences will still
be there. Any changes you make in that earlier Brackets will not be re-converted
to 36-style preferences.
use separate var names for convertedKeys & convertedKeysMap
Merge pull request #6550 from adobe/dangoor/6541-leave-prefs

Fix for #6541 that leaves preferences in place after conversion.