DRAFT: update ABAP

[jneen]

Extends #2182.
Depends on: #2256.

• Moves keywords out into a lazily-loaded file.
• Specifies @mlaggner as the primary maintainer for this keyword set. Please let me know if this is workable, otherwise let's try and write a task that generates it from the docs!
• Moves the very brittle specs out of the specs file and into the more flexible visual spec.