fetch/svn.py: use username/password when provided in SRC_URI - close OE#1781

fetch/svn.py: use username/password when provided in SRC_URI - close OE#1781

- subversion will still ask if self-signed SSL certificate will be used.
- patch looks very intrusive but some of changes were needed to be done
  to get it working properly:

  svncmd = "svn co -r {%s} %s://%s/%s" % (date, proto, svnroot, module)

  and next (now removed) lines makes BitBake ignore SVNCOOPTS which now
  provide username, password and revision in similar way to trunk version.