Update to field_table

Hi,

First of all I would like to request an analysis to the current contrib fields, because I think that several of those fields should be part of flexinode main tree. Being under contrib seems that they are discarded or so...

Anyway, the following patch (in fact it was almost a rewrite) of the field_table allows:

• an option to define the default number of rows
• an option to define the default number of columns, and their names
• the table in edit and view mode will always consider the defined columns

Further, some new things that can be done:

• option under the definition of the columns that will allow to define the kind of field editor, instead of the default "text_area" input
• validation of the input data thru those fields

Hope you like it! More work to do...

Regards,
Fernando Silva