Changing Names: Z-> W3 and C -> D3.

Buttons added to plotgraph.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git
Added comments that explain why three tests fail now
Updated test overview
Minor changes
Reference/update of illegal field now throws NoDuchField exception.
Added "non_negative" primitive for bounds checking in solve statement
Added bounds check to code for solve statement
Updated test progress
initialise uninitialised variables 

Added labels to graph.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git
Allowing multiple imports in checker of some module, for import and extend both
Merge branch 'master' of https://github.com/cwi-swat/rascal
Extended ENUM_NODE for concrete syntax trees.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git
Removed domain function on Lists, resolves #462
Uncommitted files
Updated test progress
Removed test for domain function on list
Removed another domain test