Reduce redudant code around column definitions

[GoogleCodeExporter]

There are 3 places where column definition forms are produced currently:
- action=table_create
- action=column_create
- action=column_edit

All three produce a form to set the column name, type, default values and so on.
This is more or less exactly the same code.

Then there is more or less 3 times the same code that produces SQL statements 
out of these forms to create/alter the table.

Original issue reported on code.google.com by crazy4ch...@gmail.com on 25 Dec 2013 at 8:42