Handle all falsy values appropriately

[mhoeger]

As @davidmrdavid, there are places where we do not treat falsy values as proper data and instead treat it as false.

Example: #364

These need to be addressed and proper linting rules need to be put in place to prevent this issue in the future

[ejizba]

Minor details might still change, but overall this was addressed in Azure/azure-functions-nodejs-library@9e6a842 as a part of the new programming model. I've started a doc here with more information: https://aka.ms/AzFuncNodeV4