Bugfix for https://github.com/spritebuilder/SpriteBuilder/issues/936.
Bugfix for #924 - SBP crashes when user creates another new package whilst the former new package wasn't named yet.
Also in this update: Hitting the forward delete key on an extended keyboard will show the delete dialogue.
Convenience method added to ResourceManage to get all packages.
Refactoring: Using that method first in ProjectSettingsWindowsController.
Refactoring:
Inject ResourceManager instead of accessing singleton.
Code formatted.
Removed obsolete #imports.
ProjectSettings property made strong.
Bugfix for #922 - All package could be deleted.
Merge branch 'develop' into bugfix/#936_empty_package_names

Conflicts:
	SpriteBuilder/SpriteBuilder.xcodeproj/project.pbxproj
Merge pull request #1000 from NickyWeber/bugfix/#936_empty_package_names

Bugfix for #936 - Empty package names cause trouble
Merge pull request #1001 from NickyWeber/bugfix/#924_adding_package_while_editing_name_crash

Bugfix for #924 - SBP crashes when user creates another new package whil...
Merge pull request #1008 from NickyWeber/bugfix/#922_all_packages_can_be_deleted

Bugfix/#922 all packages can be deleted