redo after merge: added footer element to window to allow sections to be rendered there
redo after merge: added footer element to window to allow sections to be rendered there

added section variable descriptions
added ability to empty a tag before injecting section into it
added ability to inject section into header or footer of a window

vagner2015/mochaui,mui/mochaui,vagner2015/mochaui,mui/mochaui,vagner2015/mochaui,mui/mochaui