Allow more options for CD

Description

1. Add more options and configuration for CD so the client can customize it easier. Basically, ContentApiOptions now will have four new options:

• ValidateTemplateForContentUrl: Enable/Disable the validation of content url. For example, this option should be set to 'false' in case client want to get url of a content folder
• FlattenPropertyModel: If this option is set to true, the response JSON will be flattened.
• IncludeNullValues: If this option is set to false, the JSON serializer will ignore all null values in the response.
• IncludeMasterLanguage: If this option is set to false, the response model of content will not contain the MasterLanguage property.

2. Support local block:

• When a page/content contains a local block and client requests this page in CD, the response model will include this block information.