Optimize memory with DBBitArray

[mateofio]

Depends on #379

I've added support for DBBitArray as a replacement for vector<bool>. This data structure again uses the same memory allocation strategy as DBString and DBArray.

Game	Ldb Size	#379	This PR
HH3	16MB	68.7 MB	68.5MB
Heroes Realm	27MB	143.3 MB	143.3MB
Violated Heroine	11MB	41.4 MB	40.6MB
Yume 2kki	1.4MB	4.9 MB	4.8MB

The overall savings here are pretty modest Lets look more closely at hh3's database with certain structs compiled out. This game has 850 skills and 2280 items.

Memory usage:

	All except troops & common events	Only Items	Only Skills
#379	3.2MB	936.5KB	354.3KB
This PR	2.9MB	651.8KB	302.0KB

So overall, we see a good % reduction in the size of items and skills. Unfortunately these don't make up a huge portion of the database, so the total win is pretty small.

Still overall, it's a net gain and could help a bit on memory constrained systems.

[Ghabry]

Nice. Any memory saving >300 KB is worth it. That's the size of one 320x240 picture. So it decreases the chance for a oom condition slightly 👍.