Using custom `hcurves` and `uhs` exporters in AELO mode

[micheles]

Here is the structure of the exported files:

# hcurves
   imt       iml       poe
   PGA  0.005000  0.913816
   PGA  0.006527  0.913455
   PGA  0.008521  0.912538
   PGA  0.011123  0.910480
   PGA  0.014521  0.906292
      ...       ...       ...
  SA(1.0)  1.202487  0.000906
  SA(1.0)  1.581743  0.000077
  SA(1.0)  2.080614  0.000000
  SA(1.0)  2.736825  0.000000
  SA(1.0)  3.600000  0.000000

# uhs
   poe  period       iml
  0.02     0.0  0.695452
  0.02     0.2  1.470866
  0.02     1.0  0.576505
  0.05     0.0  0.506614
  0.05     0.2  1.059386
  0.05     1.0  0.415925
  0.10     0.0  0.378868
  0.10     0.2  0.782419
  0.10     1.0  0.308323
  0.20     0.0  0.263694
  0.20     0.2  0.538265
  0.20     1.0  0.210463
  0.50     0.0  0.124536
  0.50     0.2  0.243294
  0.50     1.0  0.097187

You can see the new exporters in action with the commands

$ OQ_APPLICATION_MODE=AELO oq export hcurves
$ OQ_APPLICATION_MODE=AELO oq export uhs