Datasources limitations section

[zdrawku]

Define a known issues and limitations section that is covering all specifics related to adding of a Datasource within the AB.

https://www.infragistics.com/products/appbuilder/help/using-data-in-your-app

[zdrawku]

Done https://www.infragistics.com/products/appbuilder/help/using-data-in-your-app#unable-to-infer-schema-from-data

[hanastasov]

As part of this item, let's also add info for:

• Why certain endpoints are greyed out - return type is object, or there is no return type described in the definition
• Why one is not able to Select verbs != than GET/Post - see https://infragistics.visualstudio.com/Indigo_Platform/_git/AppBuilder/pullrequest/8121