Add design document for fpc with cc-tools

[osamamagdy]

This PR adds the design document and how we approach the integration project between CC-Tools and FPC

[mbrandenburger]

Thanks for submitting this great proposal! I highly support this work!

Please see a few cosmetic comments.

[munapower]

I have looked at the design document. These are my comments:

• please review sintax. There are a lot of sentences that are missing the period at the end.
• review code snippets that the indentations appear so it is easier to read. For example it should be like this:

func (f *FpcStubInterface) PutState(key string, value []byte) error {
    encValue, err := f.sep.EncryptState(value)
    if err != nil {
         return err
    }
    return f.PutPublicState(key, encValue)
 }

-In this sentence

For this, It's better to inject the fpc stub wrapper in the middle between fabric stub and cc-tools stub wrapper 2.

What does that 2 mean?

[mbrandenburger]

LGTM