Document settings required for CLI

[lindydonna]

The CLI requires various local settings that are similar to those required for building and running the -script project (see https://github.com/Azure/azure-webjobs-sdk-script/wiki). These need to be documented.

I'll start with a wiki page which should later be migrated to real product documentation.

Things to include:

• appsettings.json structure
• The fact that appsettings.json is only used locally
• How the environment variables AzureWebJobsStorage and AzureWebJobsDashboard are used
• The fact that func run runs the host, meaning that other triggered functions will also run. See Cli: Run a function from a list of functions in a functionapp locally  azure-functions-core-tools#31 (comment) for instance.
• All triggers other than HTTP require that AzureWebJobsStorage is set, because queue storage is used internally. It is possible to use the local storage emulator (via "AzureWebJobsStorage": "UseDevelopmentStorage=true"), but you may see limitations or differences in behavior.

[SyntaxC4]

@lindydonna - Can you provide a little bit more information on how to get the appsettings.json using the CLI?

[lindydonna]

I meant to assign this to myself. I'll write a wiki article with all the details, that then we can migrate to documentation along with other CLI docs.

[lindydonna]

Should document connection strings and app settings behavior of the CLI, see comment here: Azure/azure-functions-core-tools#33 (comment)

[lindydonna]

All these notes are in the published article: https://azure.microsoft.com/en-us/documentation/articles/functions-run-local