module totally revamped

  - reimplemented bsdportconfig to be prefetch/flush resource
  - most details are shifted to a new Puppet::Util::Bsdportconfig module,
  - removed $portsdir and $port_dbdir params, these are class attributes now,
  - the resource is no longer ensurable, the $ensure property was removed,
  - make -V is used internally to retrieve resource parameters,
  - make showconfig is no longer used to read current options,
  - current options are retrieved only from the options files,
  - options are written to "options.local" instead of "options",
  - options not listed by user in '$options' are not written to a file,
  - optimizations are added to reduce number of calls to external commands,
  - added validation of the $name parameter
  - unit tests adapted to new implementation