[UIMA-6293] Migrate UIMA Parent POM to GitHub

- Move tag to new location

git-svn-id: https://svn.apache.org/repos/asf/uima/build/parent-pom/tags/parent-pom-3@1883114 13f79535-47bb-0310-9956-ffa450edef68
tree: ffbe59520175d2e32089f5ca6ea8537b4c885745
  1. README.txt
  2. marker-file-identifying-parent-pom
  3. pom.xml