Support for LSP/tsserver Code Actions (#3437)

* Added tsserver and LSP code action support.
* tsserver refactors support added.
* Handling special case when new text is added after new line symbol.
* ale#code_action#ApplyChanges simplified.
* Initial attempt on LSP Code Actions.
* workspace/executeCommand added.
* Some null checks added.
* Add last column to LSP Code Action message.
* Pass diagnostics to LSP code action.

Previously ApplyChanges code was applied from top-to-bottom that required 
extra parameters to track progress and there was bug. I have changed code
to bottom-to-top approach as that does not require those extra parameters
and solved the bug.

Tested with typescript-language-server and it is working.

test/test_code_action_python.vader

@@ -0,0 +1,59 @@
+Given python(An example Python file):
+  def main():
+      a = 1
+      c = a + 1
+
+Execute():
+  let g:changes = [
+  \ {'end': {'offset': 7, 'line': 1}, 'newText': 'func_qtffgsv', 'start': {'offset': 5, 'line': 1}},
+  \ {'end': {'offset': 9, 'line': 1}, 'newText': '', 'start': {'offset': 8, 'line': 1}},
+  \ {'end': {'offset': 15, 'line': 3}, 'newText': "    return c\n\n\ndef main():\n    c = func_qtffgsvi()\n", 'start': {'offset': 15, 'line': 3}}
+  \]
+
+  call ale#code_action#ApplyChanges(expand('%:p'), g:changes, 0)
+
+Expect(The changes should be applied correctly):
+  def func_qtffgsvi():
+      a = 1
+      c = a + 1
+      return c
+
+
+  def main():
+      c = func_qtffgsvi()
+
+
+Given python(Second python example):
+  import sys
+  import exifread
+
+  def main():
+      with open(sys.argv[1], 'rb') as f:
+          exif = exifread.process_file(f)
+          dt = str(exif['Image DateTime'])
+          date = dt[:10].replace(':', '-')
+
+Execute():
+  let g:changes = [
+  \ {'end': {'offset': 16, 'line': 2}, 'newText': "\n\ndef func_ivlpdpao(f):\n    exif = exifread.process_file(f)\n    dt = str(exif['Image DateTime'])\n    date = dt[:10].replace(':', '-')\n    return date\n", 'start': {'offset': 16, 'line': 2}},
+  \ {'end': {'offset': 32, 'line': 6}, 'newText': 'date = func', 'start': {'offset': 9, 'line': 6}},
+  \ {'end': {'offset': 42, 'line': 8}, 'newText': "ivlpdpao(f)\n", 'start': {'offset': 33, 'line': 6}}
+  \]
+
+  call ale#code_action#ApplyChanges(expand('%:p'), g:changes, 0)
+
+Expect(The changes should be applied correctly):
+  import sys
+  import exifread
+
+
+  def func_ivlpdpao(f):
+      exif = exifread.process_file(f)
+      dt = str(exif['Image DateTime'])
+      date = dt[:10].replace(':', '-')
+      return date
+
+
+  def main():
+      with open(sys.argv[1], 'rb') as f:
+          date = func_ivlpdpao(f)