Make the error message a bit more explicit.

When the compat mode is enabled we report a Bacula compatible version id
for the filed protocol. But if you want things like passive mode or
plugin passing you need to disable the compat mode. Changed the error
message issued when using passive mode or plugin option passing when
talking to a Bareos filed in compat mode. This way the use a least knows
that it could also be a problem with the compat mode.
Upgrade bpipe plugin to use new plugin config parser.

Now that we use a new config parser for the mssqlvdi and python plugin
it makes sense to also let the bpipe plugin use this code. For backwards
compatability it also still supports the old plugin definitions so you
can also still restore older backups with the new plugin. Extra support
is added so that plugin options passing now also works and allows you to
override the plugin parameters.
Merge branch 'master' of https://github.com/bareos/bareos