Remove old combined openEHR and Ocean logo for the workbench.
Add icon code-generating application;

copy icons directory to openehr/apps/resources/icons/source (we'll delete after tagging);
separate out existing file-based icon code into ICON_RESOURCES and SHARED_ICON_RESOURCES classes;
 - this code still works, but now commented out in GUI_APP_ROOT and SHARED_ICON_RESOURCES in favour of the generated code.
- the generated pixmaps table is lazy-loaded, which reduces startup time a bit
Various void-safe related code cleanup
Clean-up message generating application and move messages to ../openehr/adl_tools/apps/resources/messages/source
Fix to ensure that if .cfg file doesn't parse correctly on startup, app reports a useful error and quits.
Remove icons from old location under adl_workbench/icons.

Minor changes to convert to using generated files.

Remaining bug: adl_workbench image does not appear on splash screen; the image is ok because it appears correctly on the help screen (which is an EV_INFORMATION_DIALOG).