Downgrade log4j dependency
Downgrade log4j dependency

In a81f2bf54fe4c8f09b5502d896a56f224c15634d the dependency 'log4j:log4j:1.2.12'
was updated to use 'org.apache.logging.log4j:log4j-core:2.14.1'. As this breaks
some usages of the metafacture library when using 'log4j-slf4j-impl' alongside
this downgrades the dependecy to use the newest release of 'log4j'.

metafacture/metafacture-core,metafacture/metafacture-core,culturegraph/metafacture-core,culturegraph/metafacture-core,metafacture/metafacture-core,culturegraph/metafacture-core