Standalone Packaging

This tries to consolidate the three platforms to provide a "standalone"
target that will do what is required to make an executable that will run
on other computers without Qt. This can then be bundled by whatever
scripts such as to make a windows installer or a jenkins portable.

The jenkins scripts will need to replace builds of ```gcs``` with ```standalone```
or ideally have their scripts integrated into the build environment when
possible. (See #1228)