Implement more validation checks

[iimog]

The types of biom attributes are checked in the setter functions. TypeErrors are thrown if there is a mismatch. As the constructor uses the setters types are also checked in the constructor. But there are other possible inconsistencies that are not yet checked:

• [x] keep shape correct by calculating dynamically (read only)
• [x] keep matrix_type correct by updating data on set
• [ ] all elements of rows and columns are objects containing (unique) id and metadata
• [ ] keep data correct by updating when rows or columns are set
• [ ] keep data correct by throwing an Error if it is set incorrectly
• [ ] format_url is really an url and not only a string
• [ ] date is really date time in ISO 8601 format

[iimog]

There are relationships between rows, columns, shape, data, matrix_type and matrix_element_type (and nnz). So updating one via a setter should either update the others or fail if the change is incompatible. Initialization is a special case because many values are set simultaneously so order of setting is important if there are incompatibilities.