Implement layer filtering

[morvagergely]

Closes #796.

[yannis216]

Oh we need this desperately, very nice!

[felix-ht]

it would also be nice if one could pass filters while adding a new layer - no need for two operations. Most of the code you have right now can be reused for that

[morvagergely]

it would also be nice if one could pass filters while adding a new layer - no need for two operations. Most of the code you have right now can be reused for that

I think it could be done in a different PR. I will probably be able to do it next week.

[felix-ht]

LGTM

missed formatting

[felix-ht]

please run the java formatting with

 java \  
  --add-exports jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED \
  --add-exports jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED \
  --add-exports jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED \
  --add-exports jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED \
  --add-exports jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED \
  -jar google-java-format-1.13.0-all-deps.jar -i $(find . -type f -name "*.java")

[skreborn]

@felix-ht Is there anything else that needs to get done before this is merged?

[felix-ht]

LGTM