Externalize antenna calc and wav view

[gullradriel]

In that PR I'm externalizing two apps, Antenna Length and WAV Viewer.
I also added a shell script in tools, to easily spot unused graphics files.

# Note:
If @bernd-herzog or anyone have an idea why firmware bin is bigger with those two externalized, I'm interested.

# The problem:
Firmware size before externalization (just fitting):

Space remaining in flash ROM: 352 bytes ( 0.0 %)

Firmware size after externalization (too big):

RuntimeError: SPI flash image size of 1049616 exceeds device size of 1048576 bytes

Correction

I found the error. Never forget to adjust an external app namespace.
This:

namespace ui {

Should become this:

using namespace ui; 
namespace ui::external_app::app_name {

Now the firmware space is reclaimed correctly:

Space remaining in flash ROM: 9232 bytes ( 0.9 %)

Ready to go !!

[u-foka]

LGTM