Made generic_value return the raw value when a column is defined, but there is no data block.  For example if it was defined with an html block.  Then when defining a pretty html format for a value that's already a method on the model, the underlying method is still accessible.
Added Row class that wraps an individual asset object and makes all columns accessible.
	added datagrid view helper
fixed :url option on column to run in view context; also it now supports a symbol which will be assumed to be the path helper
add :format option to column for passing a filter function (helper that will be called with the value as an input before outputting)