JSesh imported glyphs should be reloaded when the content of the hieroglyphic folder is modified

[rosmord]

Currently (due to old limitations in Java file processing), JSesh is not aware of direct changes in the hieroglyphic folder where you can put your own hieroglyphs as SVG files.

That is, JSesh will reload signs if you have the hieroglyphic folder pointing to another place on your hard drive ; it will also
load glyphs if you try to use a glyph which hasn't been loaded yet. However, if you have already a sign in memory, and
you replace the file, JSesh won't notice it until it is restarted.

It's usually not a problem, but now that Java can listen to changes in a folder, I could improve it.