Insert should not behave like upsert

[will123195]

Currently, Table.insert() is an alias of Table.save() which does an upsert.

The API should be changed to this:

• Table.insert(data) should fail if the primary key already exists.
  • db.table.create().set(data).save({insert: true})
• Table.upsert(data) alias for Table.save(data) but disallow update and insert options
• Table.create(data) factory method to create a new row to be saved/persisted later
• row.save(opts) save the changes to this row and do a recursive upsert of nested tables
  • opts.insert: error if primary key already exists
  • opts.update: error if primary key doesn't exist
• row.update(data)
  • row.set(data).save({update: true})