API File->canEdit() returns TRUE by default (not checking CMS perms)

This is a measure to support form fields and controllers
interacting with files in different contexts,
for example an UploadField used in a ModelAdmin,
or a website frontend. The check for 'CMS_ACCESS_AssetAdmin'
was too restricting. This wasn't a problem in 2.x simply because
the old FileField/Upload classes didn't respect File->can*()
permissions.
BUG: One too many brackets in _style.scss

Caused when merging 3.0 back into master
Merge pull request #913 from adrexia/fix-style-scss

BUG: One too many brackets in _style.scss
BUG:  Site Tree checkboxes and refactoring

* Increased height of site tree checkbox by 3px, so users are less
likely to miss it and load a page by mistake
* Refactored _tree.scss to make better use of SCSS, and stop repetition
of styles
Merge pull request #908 from chillu/pulls/xmldataformatter-canview

API Removed permission checks from XML/JSON data formatters
Merge pull request #914 from adrexia/refactor-sitetree

BUG:  Site Tree checkboxes and refactoring
Added composer.json
BUG: File Uploading Notifications (fixes #7883)

Put "File upload complete" and "back to folder" together. Turned 'File
upload' into a message, and updated the message styles.
Moved allowed file types into the area where users are uploading files.
This is a temporary fix until js tooltips are implemented, at which
point, these details will be shown when clicking a question mark beside
"Choose files".
Added small animation effect to files when opening iframe to edit. Now
slides down, rather than just appearing open
Linked to silverstripe/silverstripe-cms#223
BUG: DataObject::__construct() now accepts stdClass for $record
BUG: GridField add existing auto complete has no max height (fixes #7965)

Added a maxheight to the ui-autocompleter, as used in gridfield, and
specified what to do with overflow.
Merge pull request #918 from adrexia/7965-autocomplete

BUG: GridField add existing auto complete has no max height (fixes #7965)
Merge pull request #880 from adrexia/fileoverview

BUG: File Uploading Notifications (fixes #7883)
Merge pull request #870 from chillu/pulls/datalist-filterany

NEW DataList->filterAny()
NEW: Add new method "each" to SS_List and core implementors thereof
BUG: DataObject::write overwrites Created on first write
Merge pull request #921 from TheFrozenFire/bug-DataObjectCreated

BUG: DataObject::write overwrites Created on first write
Merge pull request #920 from TheFrozenFire/feature-SSListEach

API: Add new method "each" to SS_List
Merge pull request #917 from TheFrozenFire/feature-DataObjectFromStdClass

API: DataObject::__construct() now accepts stdClass for $record
NEW: Enable multiple image manipulation back-ends on the Image class
BUG: Border at top of tabs when no subtabs

This bug reappeared when branches were merged because the 3.0 version
of _style.scss had tabsets defined in different places.

This scss was inserted, but there was no idication that it was new to
master (except in the resulting css file). As these styles are declared
differently elsewhere in _style.scss, I think this declaration must
have been refactored in an earlier commit in master.