Add a 'table' option for the Form Generator

When using a namespaced model, the generator would not find the table
information needed to generate the form. This adds an option named
table, so you can pass the table name directly to the Generator.
Add a 'route' option to prevent the namespace polluting the form routes.
Change how model name is retrieved.

Following @mrsimonbennet suggestion, I changed how the table name
is retrieved from the model, to make the generators compatible with
namespaced models.
Merge pull request #242 from beijin/form-generator-table-option

Add a 'table' option for the Form Generator