[FEATURE] get method for Feature attributes

[dshen109]

Currently, checking if features exist on an attribute involves a begin... rescue block. This can get pretty repetitive for checking single features and/or setting default values in mapper scripts:

Example of current pattern:

system_type = "Residential - furnace and central air conditioner"
begin
  system_type = feature.system_type
rescue
end

I think adding a get_property method to Feature objects which can take an optional default value would help make the code cleaner and be more object oriented.

Example proposed usage:

# Returns the second argument if `system_type` doesn't exist in the feature.
system_type = feature.get_property("system_type", "Residential - furnace and central air conditioner")