Add 'Edit Columns' and 'Add Table' Controls

[tomchristie]

Adds controls for:

• 'Add Table'
• 'Edit Columns'

These are the preliminary bits of work for making the data tables actually be dynamically editable by the end user. This work ties in with #47 which made the required SQL changes in how we store and access the data.

[tomchristie]

Still remaining here...

• Validate duplicate table names.
• Validate duplicate column names.
• Delete table.
• Delete column.
• Additional basic column types.
• Column position controls.