0.4.3 Fix #92: omg - for the last couple of weeks the official builds were

all using US frequencies.  This build fixes this (and makes the build
system cleaner in general).

If you are building your own builds in the IDE you'll need to start
setting an environment variable called COUNTRY to your two letter
country code (or leave unset to get US frequencies).  See new comment
in platformio.ini.

src/MeshRadio.h

@@ -55,7 +55,10 @@
 #define CH_SPACING CH_SPACING_JP
 #define NUM_CHANNELS NUM_CHANNELS_JP
 #else
-#error "HW_VERSION not set"
+// HW version not set - assume US
+#define CH0 CH0_US
+#define CH_SPACING CH_SPACING_US
+#define NUM_CHANNELS NUM_CHANNELS_US
 #endif
 
 /**