Mod downloading (#228)

* basic template for mod downloading

* better checks for unloading?

* Mod download stuff

* debug prints

* basic UI popup for mod downloading

* change notify location + abort download

* Prevent mods from loading lua files

* cleanup, fixes, mod aborting

* use correct pipelines

* change some messages

* fix mod downloading

* not a component

* fix hardcoded changes

Co-authored-by: Federico Cecchetto <fedecek3@gmail.com>

data/cdata/ui_scripts/mods/__init__.lua

@@ -1 +1,5 @@
 require("loading")
+
+if (Engine.InFrontend()) then
+    require("download")
+end

data/cdata/ui_scripts/mods/download.lua

@@ -0,0 +1,13 @@
+Engine.GetLuiRoot():registerEventHandler("mod_download_start", function(element, event)
+    local popup = LUI.openpopupmenu("generic_waiting_popup_", {
+        oncancel = function()
+            download.abort()
+        end,
+        withcancel = true,
+        text = "Downloading " .. event.request.name .. "..."
+    })
+
+    Engine.GetLuiRoot():registerEventHandler("mod_download_done", function()
+        LUI.FlowManager.RequestLeaveMenu(popup)
+    end)
+end)