Deprecate `atom.workspaceView`
:memo: Update doc to remove workspaceView
Reflow paragraph
Add a FIXME for this workspaceView bit
Remove reference to workspaceView in window-event-handler
Remove workspaceView from PackageManager specs
:memo: Remove workspaceView from doc
Remove workspaceView references from atom.coffee
Remove workspaceView from spec-helper
Remove workspaceView references from ThemeManager
Remove workspaceView references from the window-specs
View -> Element in docs
Remove the unsubscribe spy

Sorry @nathansobo, this is making the window specs fail
Merge pull request #4248 from atom/bo-deprecate-workspace-view

Deprecate workspaceView