sim-applet: add "flash" and "remove" targets

Using wrong arguments for shadysim.py (e.g. wrong --max-menu-entry-text)
results in cryptic errors, so let's version them along with the source.
diff --git a/sim-applet/.gitignore b/sim-applet/.gitignore
index 567609b..de1e90a 100644
--- a/sim-applet/.gitignore
+++ b/sim-applet/.gitignore
@@ -1 +1,2 @@
 build/
+.sim-keys