Change the network encoding of the "move behavior" option enum from an
integer to a string as we already do for e.g. the depth option.

* subversion/include/svn_types.h
  (svn_move_behavior_to_word,
   svn_move_behavior_from_word): Declare new type<->string conversion utils.

* subversion/libsvn_subr/types.c
  (svn_move_behavior_to_word,
   svn_move_behavior_from_word): Implement these new utils.

* subversion/mod_dav_svn/reports/log.c
  (dav_svn__log_report): Use a string to encode the move behavior option.

* subversion/libsvn_ra_serf/log.c
  (create_log_body): Extract the move behavior from its string rep.

* subversion/svnserve/serve.c
  (log_cmd): Use a 'word' to encode the move behavior option.

* subversion/libsvn_ra_svn/client.c
  (perform_ra_svn_log): Extract the move behavior from the optional 'word'.

* subversion/libsvn_ra_svn/protocol
  (Main Command Set): Update log encoding command description.

Suggested by: ivan

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1572044 13f79535-47bb-0310-9956-ffa450edef68