Added "known issues", config cleanup, consolidated taglet registering

ADDED: ComSunJavaDocUtil.registerNewTagletInstance
CLEANED UP: static holding of the CodeletBootstrap.INSTANCE, for--as
much as is possible--minimizing the number of times configuration is
loaded. See "Known Issues".
FIXED: CodeletBootstrap.wasLoaded()
DOCS:
- ADDED known-issues section to overview
- ADDED more concise download list