Bump jetty.version from 9.4.30.v20200611 to 9.4.31.v20200723 in /core

Bumps `jetty.version` from 9.4.30.v20200611 to 9.4.31.v20200723.

Updates `jetty-server` from 9.4.30.v20200611 to 9.4.31.v20200723
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](https://github.com/eclipse/jetty.project/compare/jetty-9.4.30.v20200611...jetty-9.4.31.v20200723)

Updates `jetty-servlet` from 9.4.30.v20200611 to 9.4.31.v20200723
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](https://github.com/eclipse/jetty.project/compare/jetty-9.4.30.v20200611...jetty-9.4.31.v20200723)

Updates `jetty-webapp` from 9.4.30.v20200611 to 9.4.31.v20200723
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](https://github.com/eclipse/jetty.project/compare/jetty-9.4.30.v20200611...jetty-9.4.31.v20200723)

Signed-off-by: dependabot[bot] <support@github.com>

Closes #98

Change-Id: If175a5eec9a3271280be8e1a7d58f99438d4479a
diff --git a/core/pom.xml b/core/pom.xml
index d925f61..0ec909b 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -10,7 +10,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<spring.version>5.2.8.RELEASE</spring.version>
 		<jersey.version>1.19.4</jersey.version>
-		<jetty.version>9.4.30.v20200611</jetty.version>
+		<jetty.version>9.4.31.v20200723</jetty.version>
 		<hibernate.version>5.3.7.Final</hibernate.version>
 		<log4j.version>2.13.3</log4j.version>
 	</properties>