Move "clapper_src" dir to "src"

The "clapper_src" directory name was unusual. This was done to make it work as a widget for other apps. Now that this functionality got removed it can be named simply "src" as recommended by guidelines.

bin/com.github.rafostar.Clapper.Subprocess.in

@@ -14,4 +14,4 @@ Package.init({
   libdir: '@libdir@',
   datadir: '@datadir@',
 });
-Package.run(imports.clapper_src.main@ID_POSTFIX@);
+Package.run(imports.src.main@ID_POSTFIX@);

bin/com.github.rafostar.Clapper.in

@@ -9,4 +9,4 @@ Package.init({
   libdir: '@libdir@',
   datadir: '@datadir@',
 });
-Package.run(imports.clapper_src.main);
+Package.run(imports.src.main);