Added private-rows-extensions Maven project

.gitignore

.gitmodules

database/01-init.sql

database/02-tap_schema.sql

database/03-tap_schema-grants.sql

database/Dockerfile

private-rows-extensions/pom.xml

...sions/src/main/java/it/inaf/ia2/vollt/CustomJobOwner.java

...src/main/java/it/inaf/ia2/vollt/CustomUserIdentifier.java

...main/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutor.java

.../java/it/inaf/ia2/vollt/PrivateRowsQueryExecutorTest.java

vollt