Add shared gens section & invalid cryptosuite generator

[aljones15]

Features:

1. exports issueCloned
2. Adds a new shared generators section for invalid cryptosuite name tests.

[PatStLouis]

The goal here is to add a negative test for an invalid cryptosuite?

[aljones15]

The goal here is to add a negative test for an invalid cryptosuite?

that is the goal, but this PR only adds a generator so that whenever you need to create a VC signed with an invalid cryptosuite, you can use this generator or this generator combined with other generators (I created a VC with an invalid proof.type and proof.cryptosuite over in the bbs assertion). I had put this generator in shared, but after reviewing the spec it looks like this is now a mandatory D.I. generator so I'll move it to mandatory in a moment. Not sure if adding a new test to D.I. is in the scope of this PR especially with a clean up PR that changes the verify tests a lot looming.

[aljones15]

@PatStLouis @tminard I'm going to go ahead and merge this as it was approved before I was aware a test was needed for this. Anyways, I will add the test in a moment.