Add Improvers for the migrated importers

[TG1999]

• Apache HTTPD ( PR under progress Add apache_httpd improver #1102 )
• NPM ( PR under progress Add valid version improver #1138 )
• Istio ( PR under progress Add istio improver #1103 )
• Elixir_security ( PR under progress Add valid version improver #1138 )
• Apache Kafka (PR under progress Add valid version improver #1138 )
• Apache Tomcat ( PR under progress Add valid version improver #1138 )

[TG1999]

Done in #1138