Fdc3 for web impl refactor rm

[robmoffat]

@Lecss

I've:

• Removed fdc3-common
• converted all the modules to ES6
• Got all the tests working
• Split out the schema generation into it's own module

These were all related to one another, so once I started pulling on it, I just had to get to a good place.

https://github.com/finos/FDC3/issues/1297

Still things left to do

[Lecss]

Looks good and moving in the agreed direction. Will continue with the other refactor changes