tests: add a test program for lib/command.c

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
lib/command.c: rewrite command matching/parsing

Add support for keyword commands.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
ospfd/ospf_vty.c: use keyword cmd style

Use the new keyword command style for:

  - default-information originate
  - distance ospf
  - redistribute

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Merge branch 'vty-keywords' into osr/master