Fix iIntros on forall

Fixes #307 (closed) and adds support for iIntros "%x" with a named variable (as expected given the behavior of iIntros "%").

LGTM. Let's see what @robbertkrebbers says.

added 2 commits

• 057b0d0b - Fix introducing forall with "%" intro pattern
• 075aaf22 - Add support for naming forall intros

Compare with previous version

added 2 commits

• f6f5c9cb - Fix introducing forall with "%" intro pattern
• de075210 - Add support for naming forall intros

Compare with previous version

added 2 commits

• cd46e84f - Fix introducing forall with "%" intro pattern
• b49ebbb4 - Add support for naming forall intros

Compare with previous version

resolved all threads

added 2 commits

• 43453440 - Fix introducing forall with "%" intro pattern
• aca71b6b - Add support for naming forall intros

Compare with previous version

added 2 commits

• 52836fec - Fix introducing forall with "%" intro pattern
• 145045c1 - Add support for naming forall intros

Compare with previous version

added 2 commits

• 89174aca - Fix introducing forall with "%" intro pattern
• a14f0fa3 - Add support for naming forall intros

Compare with previous version

resolved all threads

Thanks a lot @tchajed :)

mentioned in commit 8a3bd004