set default_codec doc attribute

[skip ci] update gemspec summary

Version bump

For elastic/logstash#7993

[ci skip]

remove obsolete option data_timeout

bump patch level for doc generation

Update CHANGELOG.md

Limit objects accepted to be only log4j objects

Fixes #39

missing is

dependency logstash-core-plugin-api >= 1.60 <= 2.99

Make sure all the gems were published under jruby