Disable case sensitive in ORDER BY clause

This simple addition makes "order by" case insensitive (which is the default behavior with other Django db backends ;).
Merge pull request #220 from Pirhoo/patch-2

Disable case sensitive in ORDER BY clause
Moved LOVER function to orderby expression
Remove lower
Merge pull request #221 from Pirhoo/patch-2

Removed lowercase on Order By
Merge branch 'master' of https://github.com/scholrly/neo4django