Several minor tweaks

Only significant one is that the Login page now explicitly tells folks
to go click on their invite links.  That may help slightly with the
confusion I've been seeing.
InviteLink is less dependent on the Person

Checkpoint: moving towards being able to generate miscellaneous invite
links.
External links to any Thing can now carry credentials

Invite Link can now receive any Thing T; it will append the credentials
so that the email recipient gets logged in when they follow that link.
Added the Chromeless Invites property

This can be set on a Thing or Space; if set, invite links to that Thing
will be displayed chromelessly.  (I suspect it usually wants to be set
on the Space, but maybe not always.)
Added the All Properties page

This is now standard, accessible from the standard Actions menu.

To support that, added the _allProps method, which can be used from
code.
Release 0.3.15