Cleaned up existing server classes by formatting and remove/sorting usings
Moved the Payloads from the Asp.Net samples to the common test project
Modified the payloads namespace
Restricted payload attribute to only be applied to classes

- In the future we could allow for this to apply to interfaces with the following restrictions
1. The interface itself is not a PayloadDescriptor
2. Classes that implement the interface only have dataDescriptors describing the interface methods.