add macros support

Macros should be declared as `aw_macro<name,arg1,arg2,...>{{macro body}}` and then
they may be used as `aw_name<arg1,arg2,...>{{}}`. It just puts `macro
body` to pattern and replaces arguments to provided ones according to
macro call. E.g.:
```
$aw_macro<test,phrase>{{phrase}}$aw_test<hello world>{{}}
```
will transform into
```
hello world
```

sources/awesome-widget/plugin/awkeyoperations.cpp

@@ -342,6 +342,7 @@ void AWKeyOperations::reinitKeys()
     m_pattern = AWPatternFunctions::insertKeyCount(m_pattern, allKeys);
     m_pattern = AWPatternFunctions::insertKeyNames(m_pattern, allKeys);
     m_pattern = AWPatternFunctions::insertKeys(m_pattern, allKeys);
+    m_pattern = AWPatternFunctions::insertMacros(m_pattern);
     // wrap templates
     m_pattern = AWPatternFunctions::expandTemplates(m_pattern);