Prepend a slash to a path if it does not start with one. Fixes opening
rascal:// locs from stacktrace in editor.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git
Exception handling: decided when to return and when to throw 'Thrown'.
Added a few more exception handling tests.
Added a few cases to TestSuite, including those with @expected tag.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git
One more case to TestSuite.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git
Merge pull request #326 from Y3PP3R/master

Opening rascal:// locs on windows in stacktrace
Added a missing import of Exception to Set.
Implemented a missing case for splicing.

Occurrences of a splice operator in the contribution to a comprehension
were not supported, e.g., {*x | x <- [[1,2], [3,4]]}
Added missing import of Exception in ListRelation
Added missing import of Exception in Relation.
Added missing import of Exception to DateTime.
Added missing import of Exception to util/FileSystem
Added missing import of Exception to util/Webserver
Added missing import of Exception to Type.
Added missing import of Exception to util/Benchmark.
Added more missing imports of Exception.
Fixed bug in reified type expression checking, resolves #320