Add documentation
Atoms in the TLB must be unique.

There must not be duplicates; in particular, atoms not in an atomtable
cannot have a Handle.
Get rid of unused HashCode

Dead code clutters and make things complex. Lets keep things simple.
The atom handle already provides a unique ID.  If you want to use it
as a hash, then knock out a few low-order bits.
Use C++11 unordered_map instead of boost.
Remove more unused hash codes.
Remove another user of HandleEntry
Kill another HandleEntry user.
Remove the last user of HandleEntry
Get rid of HandleEntry completely.
Update project status
Merge pull request #137 from linas/less-handle-entry

Less handle entry