Many fix-ups to alt-text and image sizes in the manual.

Cherry-picked from the following commits:

- Fixed image sizes and alt-texts for crftsdwarf, kitchen, and Biologist 1411e62
- Fixed all image alts in workshop and furnace pages b1788d4
- Fixed workshop sizes (except 16x16s) and more alts 5227d08
- Fixed size for 16x16 imgs & millstone alt 5e73f2b
- Fixed fountain and clay oven size f4ec5d5

Part of PR #130