Cut first stable release (move to 1.x)

[nikku]

What should we do?

Cut 1.0 release.

Why should we do it?

Allow us to clearly separate major from minor improvements (ref).

[smbea]

We were waiting on some element template fixes/improvements. The next code freeze is January 3rd and I'll like to include the "replace with templates" with it and I still see a lot of element template issues open. Is there a specififc one I should wait for? Otherwise I'll just go ahead with it when I'm back to work @nikku

[nikku]

Just go ahead I guess. There will always be bugs.

[smbea]

Completed (https://github.com/camunda/camunda-bpmn-js/releases/tag/v1.0.0)