Fixed bug when creating a new simulation that caused bad model id errors.
Added hook.py to contain stuff for hook functions.
Changed hydrotrend post-stage hook to use new find_simulation_file function.
Changed to use new WMT_INPUT_FILE_PATH environment variable.

Changed
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* Now use WMT_INPUT_FILE_PATH as a list of paths in which to look for
  input files. The current set of paths is:
  - component db dir
  - model upload dir
  - current dir
Merge branch 'master' of https://github.com/csdms/wmt