Profile include support, round 2

[ghudson@MIT.EDU]

I've rewritten the profile include project page, based primarily on
feedback from Russ.

Glob support is gone, replaced by "include FILENAME" and "includedir
DIRNAME".  (I saw that remctl has a single directive which works for
both files and directories; I decided that asking the admin to be a
little more explicit was warranted.)

Error handling is strict about files existing and being readable.

Following remctl's lead, includedir only parses files with names
containing alphanumeric characters and underscores.

The "Open Issues" section is replaced with a "Rationale" section
briefly summarizing the discussion of open issues.

Feedback is still welcome up until Friday.  Thanks for the feedback
received so far.