Fix problem with listpicker selectionindex

Change-Id: I144b5aa7925411f378dc06395cc4b4f38e2d4a5f
Add more synchronization to the Blocks Editor to avoid project corruption.

Add more synchronization to Workspace and WorkspaceController in
attempt to prevent project corruption when switching workspaces.  When
reseting the workspace, call setVisible(false) on all renderable
blocks.

Change-Id: Icc408876319943998522f3748b22f967a2cea5a2