Add public CTF Writer API headers

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Add CTF Writer implementation

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add a CTF Writer test

The test will be ran as part of the "tests" test plan.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>