Move java dependency tomcat-embed to the crossTest configuration to remove outdated unnecessary compile time dependency.

This closes #2340

For the java libthrift, tomcat-embedded is only used in crossTests, I have moved it to crossTest configuration so the libthrift java package does not require this unnecessary dependency for compilation. Instead, the java-servlet dependency has been reintroduced in compile time. I've also taken this opportunity to update both dependenciesto a later version.
diff --git a/lib/java/gradle/environment.gradle b/lib/java/gradle/environment.gradle
index 965a908..b6cfb21 100644
--- a/lib/java/gradle/environment.gradle
+++ b/lib/java/gradle/environment.gradle
@@ -44,7 +44,7 @@
 // Versions used in this project
 ext.httpclientVersion = property('httpclient.version')
 ext.httpcoreVersion = property('httpcore.version')
-//ext.servletVersion = property('servlet.version')
+ext.servletVersion = property('servlet.version')
 ext.tomcatEmbedVersion = property('tomcat.embed.version')
 ext.slf4jVersion = property('slf4j.version')
 ext.junitVersion = property('junit.version')
@@ -67,8 +67,7 @@
     compile "org.slf4j:slf4j-api:${slf4jVersion}"
     compile "org.apache.httpcomponents:httpclient:${httpclientVersion}"
     compile "org.apache.httpcomponents:httpcore:${httpcoreVersion}"
-    //compile "javax.servlet:servlet-api:${servletVersion}"
-    compile "org.apache.tomcat.embed:tomcat-embed-core:${tomcatEmbedVersion}"
+    compile "javax.servlet:javax.servlet-api:${servletVersion}"
     compile "javax.annotation:javax.annotation-api:${javaxAnnotationVersion}"
 
     testCompile "junit:junit:${junitVersion}"