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:
+

doc/ale.txt

@@ -187,6 +187,8 @@ CONTENTS                                                         *ale-contents*
       pylint..............................|ale-python-pylint|
       pyls................................|ale-python-pyls|
       yapf................................|ale-python-yapf|
+    qml...................................|ale-qml-options|
+      qmlfmt..............................|ale-qml-qmlfmt|
     r.....................................|ale-r-options|
       lintr...............................|ale-r-lintr|
     reasonml..............................|ale-reasonml-options|
@@ -368,7 +370,7 @@ Notes:
 * Pug: `pug-lint`
 * Puppet: `puppet`, `puppet-lint`
 * Python: `autopep8`, `flake8`, `isort`, `mypy`, `prospector`, `pycodestyle`, `pyls`, `pylint`!!, `yapf`
-* QML: `qmllint`
+* QML: `qmlfmt`, `qmllint`
 * R: `lintr`
 * ReasonML: `merlin`, `ols`, `refmt`
 * reStructuredText: `alex`!!, `proselint`, `redpen`, `rstcheck`, `vale`, `write-good`