fix: supporting special missings in BETWEEN and IN operators

Impacts mp_filtercheck.sas.  Tests added.  Closes #279

sasjs/sasjsconfig.json

@@ -67,7 +67,7 @@
     },
     {
       "name": "server",
-      "serverUrl": "",
+      "serverUrl": "https://sas.4gl.io",
       "serverType": "SASJS",
       "httpsAgentOptions": {
         "allowInsecureRequests": false
@@ -107,4 +107,4 @@
       "contextName": "SAS Job Execution compute context"
     }
   ]
-}
+}