Fixes #4416 Implement recipient/endpoint shell script (#4688)

* Fixes #4416 implement shell script endpoint

* removed debugging code

* Removed for windows env

scripts/plugins/endpoints/shell_alert_endpoint/http_lint.lua

@@ -0,0 +1,25 @@
+--
+-- (C) 2020 - ntop.org
+--
+--
+
+-- Place here the checks for parameters used by this plugins
+-- In essence it extends (and references) checks present in
+-- scripts/lua/modules/http_lint.lua
+--
+
+local script = {}
+
+
+-- ##############################################
+
+-- @brief Called by the main http_lint module to load additional parameters.
+-- @params http_lint a reference to the scripts/lua/modules/http_lint.lua module
+-- @return a (possibly empty) table with parameter_name -> validator mappings
+function script.getAdditionalParameters(http_lint)
+   return {}
+end
+
+-- ##############################################
+
+return(script)