Enforce build with Java 11 for all by default

- Build with JDK11 and language levels (source and target) are now
enforced in .bazelrc, which depends on our own Java toolchain (defined
in tools/build/bazel/BUILD)
- Easymock bumped to v4.0.2 with support for Java 11 (minor API changes)
- The minimum required Bazel version is now 0.27.*

Change-Id: I0bb6dfe7fc1ea134b5a53dd249c369d58259688c
diff --git a/tools/dev/bin/onos-gen-bazel-project b/tools/dev/bin/onos-gen-bazel-project
index 0c33da1..355193a 100755
--- a/tools/dev/bin/onos-gen-bazel-project
+++ b/tools/dev/bin/onos-gen-bazel-project
@@ -3,7 +3,7 @@
 
 import subprocess
 
-JAVA_LANGUAGE_LEVEL = 8
+JAVA_LANGUAGE_LEVEL = 11
 
 EXCLUDE_DIRECTORIES = (
     "target",