Fix build by adding dependency to commons-lang3.

Classpathes in Eclipse are different from classpathes in Gradle due to
Gradle's 'implementation' configuration which does not provide
dependency transitively in Gradle.

pdb-plotting/build.gradle

@@ -5,6 +5,7 @@ dependencies {
   implementation project(':pdb-utils')
 	implementation lib_primitive_collections
 	implementation lib_jackson_databind
+	implementation lib_commons_lang3
 	
   implementation lib_log4j2_core
   implementation lib_log4j2_slf4j_impl