TLA revisited (#2990)

* Add the TLA+ language

This patch adds support for the TLA+ specification language.

https://github.com/search?utf8=%E2%9C%93&q=MODULE+extension%3Atla&type=Code&ref=searchresults

* Update TLA grammar license

Attribution is given in the license since the grammar is based off of the TLA+ language developed by Microsoft and HP.

* Sort languages.yml alphabetically

* Removing duplicate entry

vendor/licenses/grammar/TLA.txt

@@ -0,0 +1,26 @@
+---
+type: grammar
+name: TLA
+license: mit
+---
+The MIT License (MIT)
+
+Copyright (c) 2013 Microsoft and HP
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.