This patch adds support for directional links in libimagentrylink.
A directional link is added to the same header as the "internal" links,
which are unidirectional.
The "outgoing" link is added in "links.to", the "incoming" links are
added to "links.from".
This way we can always traverse all linkage. The `Linkable::links()`
method is changed to always return _all_ link.
The `Link` type was extended for notions of "to" and "from" links.
Also adds testing.
Signed-off-by: Matthias Beyer <mail@beyermatthias.de>
This patch removes the annotateable linking feature from libimagentrylink.
It was not used anyways.
Also, this patch rewrites the complete linking code to use the
toml-query "typed" feature rather than constructing everything by
itself.
This removes a lot of unmaintainable boilerplate code.
Signed-off-by: Matthias Beyer <mail@beyermatthias.de>
