open reasonable file from working set or show the no editor when an image has been deleted from the project tree.

fix 5669 [preview image] Still showing the image from prior project after opening a new project. https://github.com/adobe/brackets/issues/5669
formatting nits reported by @RaymondLim
For #5589, when switching to no editor or the image viewer, explicitly blur the old editor's hidden input field before hiding it to avoid a problem with CM's polling mechanism
fix 5696 - Thanks @larz0
Merge branch 'master' into couzteau/fix-5673

Conflicts:
	src/editor/EditorManager.js
EditorManager now only shows a document from the working set if we are not showing a new image already
Merge pull request #5697 from adobe/nj/issue-5589

Blur editor's input field before hiding the editor
Merge pull request #5683 from adobe/couzteau/fix-5673

fix 5673 - [preview image] After deleting an image file in side bar, selection moves to parent folder and image is still showing.
No redrawing of the same image if it is already open.
Merge pull request #5707 from adobe/couzteau/fix-5696

fix 5696 - working-set-header and project-dropdown-toggle bleed into the image holder
Merge pull request #5711 from adobe/rlim/skip-unneeded-redraw

No redrawing of the same image if it is already open.