ticket:10145: Updated readme for 51.2.

git-svn-id: http://source.icu-project.org/repos/icu/icu4j/branches/maint@33701 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10145: Updated some eclipse plug-in build files.

git-svn-id: http://source.icu-project.org/repos/icu/icu4j/branches/maint@33702 251d0590-4201-4cf1-90de-194747b24ca1