Support an ability to specify underly type in MemberPropertiesAttribue

[makotogitdev]

We should support an ability to specify data type to be documented for a member. For example, we should give a flexibility to allow developers to specify System.Guid type to be shown as just string(36).

[makotogitdev]

Back to the System.Guid example, Swaggeratr shouldn't force all System.Guild type to be shown as string(36), as it could be formatted in different ways. Thus adding "UnderlyingType" property approach.

http://stackoverflow.com/questions/968175/what-is-the-string-length-of-a-guid