Updated CommandCell interface with changes recommended by John.  Simplified UrlCommand Cell work.  Changed up synchronization a bit.  Added Commented out tests for expandurl with variable input.  Needs looking into.  Think about expanding locally during execute only, when needed.  Added methods for NCubeGroovyExpression.
Merge pull request #20 from kpartlow/master

Updated CommandCell interface with changes recommended by John.  Simplif...