[PSA] Configure "Save Actions" only for Java files

[Aljoscha Krettek]

If you're using "Save Actions" to auto-format your Java code, as 
recommended in [1], you should add a regex in the settings to make sure 
that this only formats Java code. Otherwise you will get weird results 
when IntelliJ also formats XML, Markdown or Scala files for you.

Best,
Aljoscha
[1] 
https://ci.apache.org/projects/flink/flink-docs-master/flinkDev/ide_setup.html#code-formatting