Much faster serializing with compression and xdr off
Add notes to TODO re optimisation
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
Merge branch 'rds2' into rds2-fast

* rds2:
  simpler length for RDS2
  Remove object list error from TODO
fix bug in paths when initialising with existing RDS2 db
don't forget to load filehash in todo sample code
add optimised dbExists method for RDS2

* can do this faster by inspecting environment directly
faster objectFile

* first check cached environment rather than always recalculating path
Merge branch 'rds2' into rds2-fast

* rds2:
  faster objectFile
  add optimised dbExists method for RDS2
  fix bug in paths when initialising with existing RDS2 db
a few more notes in TODO about performance
Merge remote-tracking branch 'jefferis/rds2-fast' into rds2

* jefferis/rds2-fast:
  a few more notes in TODO about performance
  faster objectFile
  add optimised dbExists method for RDS2
  don't forget to load filehash in todo sample code
  fix bug in paths when initialising with existing RDS2 db
  Add notes to TODO re optimisation
  Much faster serializing with compression and xdr off