Added Get<T> method to columns collection for retrieve column by expression.
Fix gridmvc.lang.fr.js 

git-svn-id: https://gridmvc.svn.codeplex.com/svn/GridMvc@30187 2abf6ff4-378a-4344-b6f7-2bcd8b316ba9
Preventing  NullReferenceException when rendering cell value #1409

git-svn-id: https://gridmvc.svn.codeplex.com/svn/GridMvc@30188 2abf6ff4-378a-4344-b6f7-2bcd8b316ba9
Merge remote-tracking branch 'remotes/git-svn'