[Dev] chandlerdb updated (0.6-16)

[Andi Vajda]

After your next 'svn update' you need to get the latest chandlerdb version by
running in 'chandler':
    make chandlerdb  - OR -
    make install

These changes add support for abstract sets of bi-directional references.

As an example I changed InclusionExclusionCollection's 'set' attribute to be 
a DifferenceSet which sets the 'appearsIn' attribute of its members to the 
InclusionExclusionCollection instances they appear in.

Andi..