Make Hazard & Risk calculation mode names consistent

[favalex]

To reflect similar changes in openquake (see https://github.com/gem/openquake/issues/190) there should be only three calculation modes, named, for both risk and hazard:

• Classical
• Event Based
• Deterministic

[favalex]

Resolved by:

• https://github.com/gem/openquake-server/pull/49
• https://github.com/gem/openquake-server/pull/50