Inconsistency between both forms of writing app settings

### Issue Details

If you attempt to add an app setting with an empty string or a JSON value of true/false, Visual Studio will not validate the deployment as correct. Through looking at the json that defines these properties, this seems coherent. However, both of those settings are valid app settings and accepted correctly if you add them under the siteConfig property.
### Repro steps (_if necessary, delete otherwise_)
1. Create template with appsettings under the siteConfig property of a web site (everything in 2015-08-01 api)
2. Add an app setting with a value of true, not "true"
3. Add an app setting with an empty string
4. Deployment works
5. Replace the siteConfig appsettings with a "type": "config" resource
6. Add both the app settings mentioned
7. Both fail to validate

Start with the issue's repro steps and compare validation of siteConfig appsettings with the separate "type": "config" resource in the 2015-08-01 API templates. Done means both forms accept app settings whose values are an empty string or the JSON booleans true and false, while deployment validation remains correct.

Written by the indexing model from the issue text.