* binding-utils.scm: add `and=>%` (`and=>` for foreign pointers).
* fs/progress-info.scm: bug fix: on '(#:publish #:complete) do not assert any
more there’s a SKS URI (we don’t always publish in a
namespace).
* examples/search.scm: add a one-line help message.
* examples/search-ns.scm,
examples/publish.scm: typos.
* identity.scm: `open-identity-service` now throws an exception on failure.
* binding-utils.scm: just add `destructuring-bind`.
* common.scm: `time-rel` now throws an exception instead of returning a
meaningless negative result; add `setup-log`.
* container/metadata.scm: `metadata-set!` now throws an exception on error.
* tests/container-metadata.scm: add tests for `metadata-copy`,
`metadata-clear`, `metadata-equal?`
and `add-publication-date!`
* identity.scm: complete bindings of GNUNET_FS_IDENTITY
* fs.scm: add support for egos/namespaces to `start-publish`
* binding-utils: remove the useless import of `assert`