update SpringBoot to 2.1.9

Also remove direct dependencies to log4j-api and log4j-core where
possible. log4j-slf4j-impl is enough in many cases.

data-store/build.gradle

@@ -10,7 +10,6 @@ dependencies {
 	compile lib_primitive_collections
 	compile lib_commons_lang3
 
-    compile lib_log4j2_core
     compile lib_log4j2_slf4j_impl
 }