[EXPORT] EmBlocks EIX plugin support

The plugin is available at:

http://www.emblocks.org/downloads/EIXplugin.7z

Copy the content inside an EmBlocks 2.20 installation. You can drag&drop Mbed generated EIX files into EB or use the Import... file menu.

This version is tested on all the projects from the export_test. The Cpp options are set by the Mbed script on file level so that it will give warning free builds. In the final version this can by overruled so that file level options are not allowed.

The STM32 targets are also tested inside the debugger.