[New_builder] Merging templates

fixed_for_next_build
new_builder

#1

Summary: Selecting a template in the new builder and then going to select a different one merges both of them. Placing places both as separate structures but overlapping.

Expected Results:
Only the second selection is active.

Actual Results:
Both selections stay active and get placed together.

Version Number and Mods in use: r-841