New issue: Configurations are not mutable

[David M. Lloyd]

It appears from what I can see in the Jigsaw code, that once a 
Configuration is calculated, it cannot be changed in any way, which 
makes them unsuitable for use in containers which add and remove modules 
at run time.  It is not clear how such containers are expected to 
function.  If there is a deliberate intention that the Jigsaw system 
will not support dynamic modification of layers/configurations 
(including the dynamic addition and removal of modules at run time), 
then that should be explicitly stated.

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- DML