removeLayer was clearing all the overlay layers..

...from the layer control.  The fail was happening because groupContainer on line 225 was not null, so the "// Create the group container if it doesn't exist" section will never be executed
Made basic example more hackable

- Removed closure so things can be played with at the console.
- Assigned the layer control to a variable to test add/remove functions.
- Converted tabs to spaces to fix indentation issues.
Documented how to add a layer

- Replaced tabs with spaces to fix indentation issues.
Moved _domGroups reset to _update

- The _update function recreates the layer control element, so the _domGroups array needs to be cleared anythimg _update is called.
Merge branch 'pr/n4_blomm'
Converted tabs to spaces