Added SetForceCompactMode() for overriding the compact setting...

...on a per-node level. All sub-nodes will be printed compact as well. As discussed in #157. I'd be happy with just this, but for my content it would also work if any block that has a text child as its first or last child got this flag turned on automatically. Just not sure whether this could cause problems for anyone else, so leaving the final decision up to you.