oq-engine-server: Implement `calc info` views

[Lars Butler]

When a client hits /calc/hazard|risk/:calc_id, return info about the calculation, including:

- id
- status
- description
- all calculation parameters

Hazard example:
{"status": "complete", "reference_depth_to_1pt0km_per_sec": 100.0, "mean_hazard_curves": true, "id": 1, "reference_vs30_type": "measured", "maximum_distance": 200.0, "sites": {"type": "MultiPoint", "coordinates": [[0.5, -0.5]]}, "width_of_mfd_bin": 0.1, "intensity_measure_types_and_levels": {"PGA": [0.005, 0.007, 0.0098, 0.0137, 0.0192, 0.0269, 0.0376, 0.0527, 0.0738, 0.103, 0.145, 0.203, 0.284, 0.397, 0.556, 0.778, 1.09, 1.52, 2.13]}, "area_source_discretization": 5.0, "investigation_time": 50.0, "poes": [0.1], "uniform_hazard_spectra": true, "random_seed": 23, "description": "Classical PSHA with non-trivial logic tree (2 source models and 2 GMPEs per tectonic region type)", "number_of_logic_tree_samples": 0, "truncation_level": 3.0, "quantile_hazard_curves": [0.05, 0.5, 0.95], "reference_depth_to_2pt5km_per_sec": 5.0, "reference_vs30_value": 600.0, "calculation_mode": "classical", "no_progress_timeout": 3600, "hazard_maps": true, "rupture_mesh_spacing": 2.0}

Risk example:
{"status": "executing", "hazard_output": 185, "quantile_loss_curves": [0.3, 0.5], "maximum_distance": 5.0, "description": "Classical PSHA Risk Demo", "insured_losses": false, "lrem_steps_per_interval": 5, "loss_curve_resolution": 50, "calculation_mode": "classical", "no_progress_timeout": 3600, "conditional_loss_poes": [0.1, 0.2, 0.3], "region_constraint": {"type": "Polygon", "coordinates": [[[-1.5, 1.5], [0.5, 1.5], [0.5, 0.5], [-1.5, 0.5], [-1.5, 1.5]]]}, "asset_correlation": 0.0, "id": 1}

[Lars Butler (lars-butler)]

Pull request: https://github.com/gem/oq-engine-server/pull/2

[Lars Butler (lars-butler)]

We should probably also update this to include the lib/software version, per the changes here: https://github.com/gem/oq-engine/pull/1232