Use the latest m4 (#674)

* Add databricks, fix several issues

* Fixed a completer related issue and add support for credential

* Add two m4 configuration and fix some issues

* Add support for enum with one value

* Fixed an enum related issue and add some RPs in the test

* Fix some issues in m4 test

* just for test, do not merge

* Update autorest-configuration.md

Author: dolauli

powershell/autorest-configuration.md

@@ -11,14 +11,16 @@ modelerfour:
   lenient-model-deduplication: true
   additional-checks: false
   always-create-content-type-parameter: false
+  always-seal-x-ms-enums: true
 ```
 
 > if the modeler is loaded already, use that one, otherwise grab it.
 
 ``` yaml 
 use-extension:
   "@autorest/remodeler" : "~2.1.0" 
-  "@autorest/modelerfour": "4.15.378"
+  #"@autorest/modelerfour": "4.15.378"
+  "@autorest/modelerfour": "http://tinyurl.com/y2r8qhs4"
 
 # will use highest 2.0.x 
 ```
@@ -468,4 +470,4 @@ cli:
             choiceValue:  'pascal'
             constant:  'pascal'
             type:  'pascal'
-```
+```