F2FS support for fastboot format and fsmgr

- Enables fsck.f2fs for partitions with type F2FS.
- Adds support for f2fs as format fs-type.
- f2fs is optional and support is dlopen()d when needed.

Needs changes in
  system/extras/f2fs_utils
  external/f2fs-tools

Change-Id: I8d141a0d4d14df9fe84d3b131484e9696fcd8870
Signed-off-by: JP Abgrall <jpa@google.com>