[AgileWiki] Updated all Columns tables, more types of structures

[Bill la F. <bil...@su...>]

I've now updated the Columns table in the following descriptor units:

    * SimpleAccountingDescriptorUnit,
    * UsersDescriptorUnit and
    * ColumnsDescriptorUnit.

For each row in the Columns table, there is now an optional field type 
name and an optional required flag. And I think the next step is na 
obvious one: update the crRow and editRow commands to validate based on 
this additional information.

Now it occurs to me that while the LEnts of a Rolon can be described as 
a structure, the same is always true of DEnts and CEnts. So perhaps 
every descriptor unit should have a DStruct and a CStruct table to 
define these structures? With this addition, suddenly AgileWiki becomes 
a strongly typed system.

Bill