Integration of qmlfmt linting tool (#1462)

* Add first qmlfmt support

* Add GetCommand() function

- pass --error/-e option

* Add handle unittest

- fix pattern regex
- store col as integer

* Update docs

* Add command callback unit test

doc/ale-qml.txt

@@ -0,0 +1,18 @@
+===============================================================================
+ALE QML Integration                                           *ale-qml-options*
+
+
+===============================================================================
+qmlfmt                                                         *ale-qml-qmlfmt*
+
+g:ale_qml_qmlfmt_executable                       *g:ale_qml_qmlfmt_executable*
+                                                  *b:ale_qml_qmlfmt_executable*
+  Type: |String|
+  Default: `'qmlfmt'`
+
+  This variable can be set to change the path to qmlfmt.
+
+
+===============================================================================
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:
+