streamFiles 2nd argument is now optional.  fix segfault that was happening with originate/bridge due to no valid session in b leg.  rename streamfile to streamFile.  remove playFile since streamFile does the same thing

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@5454 d0543943-73ff-0310-b7d9-9358b9ac24b2