Build and test against JPA 2.2 and EclipseLink 2.7 (while retaining compatibility with JPA 2.1)

Includes latest dependency updates (Tomcat 8.5.20, Protobuf 3.4, RxJava 2.1.3, Caffeine 2.5.5)

Issue: SPR-15870

build.gradle

@@ -40,8 +40,8 @@ configure(allprojects) { project ->
 	ext.aspectjVersion         = "1.9.0.BETA-6"
 	ext.beanvalVersion         = "2.0.0.Final"
 	ext.cacheApiVersion        = "1.0.0"
-	ext.caffeineVersion        = "2.5.4"
-	ext.eclipselinkVersion     = "2.6.5-RC2"
+	ext.caffeineVersion        = "2.5.5"
+	ext.eclipselinkVersion     = "2.7.0-RC3"
 	ext.ehcacheVersion         = "2.10.4"
 	ext.ehcachejcacheVersion   = "1.0.1"
 	ext.ehcache3Version        = "3.3.1"
@@ -66,7 +66,7 @@ configure(allprojects) { project ->
 	ext.jettyVersion           = "9.4.6.v20170531"
 	ext.jmsVersion             = "2.0.1"
 	ext.jodaVersion            = "2.9.9"
-	ext.jpaVersion             = "2.1.1"
+	ext.jpaVersion             = "2.2.0-RC3"
 	ext.jsfVersion             = "2.2"
 	ext.jsonassertVersion      = "1.5.0"
 	ext.jspVersion             = "2.3.2-b02"
@@ -80,20 +80,20 @@ configure(allprojects) { project ->
 	ext.niomultipartVersion    = "1.1.0"
 	ext.okhttp3Version         = "3.8.1"
 	ext.poiVersion             = "3.16"
-	ext.protobufVersion        = "3.3.1"
+	ext.protobufVersion        = "3.4.0"
 	ext.quartzVersion          = "2.3.0"
 	ext.reactorVersion         = "Bismuth-BUILD-SNAPSHOT"
 	ext.romeVersion            = "1.7.4"
 	ext.rxjavaVersion          = '1.3.0'
 	ext.rxjavaAdapterVersion   = '1.2.1'
-	ext.rxjava2Version         = '2.1.2'
+	ext.rxjava2Version         = '2.1.3'
 	ext.rxnettyVersion         = '0.5.2'
 	ext.servletVersion         = "3.1.0"
 	ext.slf4jVersion           = "1.7.25"
 	ext.snakeyamlVersion       = "1.18"
 	ext.testngVersion          = "6.11"
 	ext.tiles3Version          = "3.0.7"
-	ext.tomcatVersion          = "8.5.19"
+	ext.tomcatVersion          = "8.5.20"
 	ext.tyrusVersion           = "1.13.1"
 	ext.undertowVersion        = "1.4.18.Final"
 	ext.websocketVersion       = "1.1"