GSW: Updated Build System for Examples.
The example build system compiles all examples in the
GettingStartedWithWhiley guide.  Currently, it is very incomplete.
However, I have now added the examples for the introduction and
walkthrough sections.  This identified a number of bugs in those
examples, which I have now corrected.
Merge branch 'master' of github.com:Whiley/WhileyDocs