pass invalid namespaces up to executor as it keeps it's own list
catch ex CS0246 and extract namespace
added a const for CS0246
added extra null check and Any() check
added tests
changed InvalidNamespaces property to be immutable and backed by a field
Merge pull request #850 from filipw/bugfix/849

Prevent incorrect namespace from breaking your REPL
Added failing test case
Fixed bug
version 0.11.0