prepare for release

RELEASE_NOTES.txt

-Release 2.3.1 (XX/YY/2019)
+Release 2.4.0 (05/20/2019)
 =============================
 - Added system LDAP utilities for verifying and creating groups
 - Added support for retrieving single processing job stage via the --stage
   option for the get-processing-job command
 - Prevented core files from being uploaded
 - Prevented creation of experiment names with spaces
+- Fixed file limit problem in compression utilities
+- DM Station GUI fixes/enhancements:
+  - Fixed issue with experiment user list modification
+  - Added tab for monitoring processing jobs
+  - Restored workflow tab 
 
 Release 2.3.0 (04/15/2019)
 =============================