Switch to use an environment to keep track  of objects

* environments are never duplicated so this takes care of the problems with
  not being able to set slot contents from inside methods
fix bugs in insertion and deletion to objectlist envir
Merge branch 'rds2' into rds2-fast

* rds2:
  fix bugs in insertion and deletion to objectlist envir
  Switch to use an environment to keep track  of objects
Remove object list error from TODO
simpler length for RDS2

* since length returns the number of objects in environment
Merge branch 'rds2' into rds2-fast

* rds2:
  simpler length for RDS2
  Remove object list error from TODO