BL-663 Predefine Heading1 and Heading2 styles

Several other changes enable this.
- Replace defns of heading1 and heading2 in editMode.css
- Make the style finder smarter about only styles ending in -style,
  and ignoring anything before the last dot.
- When a style is first applied, copy its explicit settings
  into user-defined and make them !important.
Merge pull request #102 from JohnThomson/HeadingStyles

BL-663 Predefine Heading1 and Heading2 styles