Should be able to operate directly on `Table` columns

Should be able to:

• Add/modify a column using a list of values. Example: table['new_column'] = [i ** 2 for i in range(len(table))] (assert len(new_column_values) == len(table)).
• Add/modify a column using a function which receives Row as parameter. Example: table['new_column'] = lambda row: row.some_value ** 3.
• Provide a method to add/modify a column so we can insert it in the desired position (Table.fields is a collections.OrderedDict).
• Delete a column. Example: del table['some_column']

Questions:

• What to do about the new field type in case of adding/modifying using list of values/function? Options: 1- simply auto detect (involves more processment); 2- list of values or function returns instance of type (overkill); 3- use a tuple to associate the new column (example: table['new_column'] = rows.fields.IntegerField, [i ** 2 for i in range(len(table))]).

Related to #60.

Start with the Table and Row APIs, especially Table.fields, and review related issue #60. Define how list- and function-based column updates should handle field types and ordering, then verify that adding, modifying, inserting, and deleting columns meet the requested examples.