Move list of operations to the Thing Description specification

[benfrancis]

The WoT Architecture currently provides a table of "well-known operation types for the Web of Things" in section 8.6.2 Forms.

We discussed on multiple calls that this table should be moved to the Thing Description specification, since that specification provides the canonical list of op types in section 5.3.4.2 Form.

Currently every time a new operation type is added, the name has to be added to the Thing Description specification and then a description added to the architecture specification and the two have to be kept in sync.

[egekorkan]

Duplicate of #606

[benfrancis]

Aha, thanks!