Merge branch 'martinal/topic-improve-mesh-svg-rendering'
Merge branch 'martinal/topic-add-enabled-coefficients-per-integral'
Don't allow passing a SubDomain to *_domains arguments to assemble*.

This feature has been silently broken for a while and was always unclear.
Fix tests in Form.py using the removed SubDomain assembly feature.
Fix SystemAssembler in C++ to pick subdomains from a or L properly.
Merge branch 'martinal/fix-issue-78' into next
Merge branch 'martinal/fix-issue-226-disallow-subdomain-in-assemble' into next