API endpoints misunderstand non-stringified numerical inputs

[corviday]

The backend is usually called with a URL, such as https://services.pacificclimate.org/pcex/api/multistats?ensemble_name=ce_files&model=PCIC12&variable=cdd&emission=historical,rcp85&time=0&timescale=seasonal

In this case, the API automatically receives the parameters as strings, since a URL is a string. The value of the time parameter for the multistats() function run by the above URL will be "0"

However, the API functions are sometimes called directly by other python programs processing data. In this case, the time parameter would most naturally be specified as an int 0 instead of a string "0". This produces unpredictable results because several of the API endpoints check to see whether or not a parameter has been supplied with something like this:

if time:
  # do something involving the time value
else:
  # do something without the time value

If the API is called from a URL with the value stats?time=0, the code above will directly determine that there is a value supplied for time and do something with that value. However, if it is called directly by another python program as stats(time=0) the time parameter will be falsy and the without-time-value action will happen instead.

Ways a parameter might be specified or not to the API:

1. a URL that doesn't mention the parameter at all
2. a URL that mentions the parameter but doesn't supply a value
3. a URL that mentions the parameter and supplies a value
4. a direct call that doesn't provide a value
5. a direct call that does provide a value

I believe right now the backend handles the first four correctly, but not the fifth in the case of numeric parameters equal to 0.