Bugfixes in Command-line SPT transform expectation evaluation.

[AZWN]

This PR fixes the following issues:

• Bugs in SPT transformation expectation evaluation:
  • Pass proper Context(File) parameter
  • Pass proper Context(Project) parameter
  • Use regular selections, which correspond to the offsets seen by the object language parser.
• Spoofax CLIs now give error codes when the underlying command fails. (no distinction between different errors is made (yet)).
• CLI commands that execute test now print the total number of passed/failed test cases.
• Some classes that are used in serialized configuration now implement Serializable, preventing errors.
• In code completion, delayed queries are removed from the active constraint set, fixing non-termination issues.

The non-trivial changes are documented with inline comments.

[AZWN]

Fixes #130

[Apanatshka]

Please update the CHANGELOG.md with your changes, then feel free to merge.