compliance bug fixes and more tests

- break first paragraph of list item at start of any other list
- support quotes around first positional attribute
- optimize regular expressions for lists
- only increment block counter for blocks that have a generated caption
- make default value of iconsdir consistent w/ AsciiDoc
- optimize next_block loop
- register id for sections, not just when section id is generated
- promote more inline regexps to constants
- further document differences from AsciiDoc