Add body parsing for subject keywords

[atla5]

TableOfContents, and Contributors are examples of elements that tend to be added en masse, and that was the reason I devoted so much of the body to them.

Subject is another one of these that could benefit from bulk processing, and the change may be a large added value/feature, especially in the absence of a quality OCR scan (or bPress database) :p

questions would be whether or not...

• to remove it from the "options.txt" table then (prevent adding them inline for consistency).
• i'd have to change the strategy for determining qualifiers (EDITOR vs ARTIST, KEYWORD vs. LCSH).*
• i'd have to create a bunch of synonyms for "subject", "keyword", etc. to make it sensible.

*LCSH codes don't have to include lowercase letters and would often match the current criteria for a qualifier switch

ex:

-SUBJECTS-
KEYWORDS/TAGS
dogs
cats
fish
LCSH
QA76.
DDC
LCC
MESH
UDC

[atla5]

won't remove it from the inline parsing for now. don't see a need.