Added pre/post build view event
Renamed ColumnView to CellView
Added Column Header View objects to DataGrid View
Fix SymfonyFormExtension bindData method.
Fixed documentation for columns.
Merged in beregond916/datagrid/doc (pull request #2: Fixed documentation for columns.)
Fixed wron private field name in DIExtension class
Updated README to support the latest changes.
Sort columns only when at least one of them have order attribute different from 0.
Added "format" option
Added reverIndex method to IndexingStrategyInterface
Added information about tests to README
Removed useless Sekable Interface from DataGridRowView
Added Boolean column type
Addd "empty_value" option
Updated core types to support empty value
Added Boolean column type documentation
Fix bindData method
Fixed Core/ActionExtension class name
Fixed line delimiters