Initial logstash package build in spksrc

Logstash Package created in spksrc for the SynoCommunity.
We do not make assumption on how the configuration and log files will be edited or viewed by the user, it's always under the `${PACKAGE_DIR}/var` for all our packages with backup/restore on update. If one wants to change it, fine, a few SSH commands will do the job. Live editing is easy with tools such as scp.

I guess a wizard could be useful to tell the user where the config / log files are i.e. /usr/local/logstash/var