fix(formatting): Make formats parse specs as-is

This removes the spacing tinkering when parsing format specs.
The following example uses the old behavoir:

    format-test = <label-foo>  <label-bar>
    format-breaks = <label-foo><label-bar>/<bar-test>

`format-test` would replace all occurences of ' ' with the
a space string with defined `spacing` as its width. `format-breaks` would
not validate as the tags where split with ' ' as delimiter.

All that nonsense has been removed and each tag is extracted as is.
The `spacing` parameter can still be used to apply N extra whitespaces
between the tags, but it is now 0 by default.

src/modules/xkeyboard.cpp

@@ -100,7 +100,7 @@ namespace modules {
   bool xkeyboard_module::build(builder* builder, const string& tag) const {
     if (tag == TAG_LABEL_LAYOUT) {
       builder->node(m_layout);
-    } else if (tag == TAG_LABEL_INDICATOR) {
+    } else if (tag == TAG_LABEL_INDICATOR && !m_indicators.empty()) {
       size_t n{0};
       for (auto&& indicator : m_indicators) {
         if (n++) {