Remove GBL.  GBL and hps-dst are separate packages being developed by independent groups and should remain so.  Instead, users should download and build GBL themselves. If a user chooses not to install GBL, the GBL collections will be included in the DST.
Fix dependencies and remove unnecessary forward declarations
Formatting and cleanup
Fix dependencies and remove unnecessary forward declarations
GBL is now a required to build hps-dst.  After GBL is installed, the user defined environmental variable GBL_DIR allows cmake to find the GBL config that sets some cmake variables.  Some dependencies were also fixed