SAML support (#3494)

* PLT-3073: Implement SAML/Okta Server side (EE) (#3422)

* PLT-3137 Support for SAML configuration

* PLT-3410 SAML Database Store

* PLT-3411 CLI to add Identity Provider Certificate and Service Provider Private Key

* PLT-3409 SAML Interface for EE

* PLT-3139 Handle SAML authentication server side

* Add localization messages

* PLT-3443 SAML Obtain SP metadata

* PLT-3142 Login & Switch to/from SAML

* Remove Certs for Database & Clean SAML Request

* Make required Username, FirstName and LastName

* PLT-3140 Add SAML to System Console (#3476)

* PLT-3140 Add SAML to System Console

* Move web_client functions to client.jsx

* Fix issues found by PM

* update package.json mattermost driver

* Fix text messages for SAML

glide.yaml

@@ -39,3 +39,4 @@ import:
 - package: gopkg.in/throttled/throttled.v1
   subpackages:
   - store
+- package: github.com/kardianos/osext