programmable activators

[ammen99]

Still WIP, but should eventually:

fix #655
fix #833

This PR adds the long-awaited support for calling arbitrary plugins via their activator bindings. Example patch to make Expo activate on all workspaces at the same time (although I recommend actually doing an external plugin which activates all Expos on all outputs):

diff --git a/plugins/single_plugins/expo.cpp b/plugins/single_plugins/expo.cpp
index 2d4e11b6..8092898b 100644
--- a/plugins/single_plugins/expo.cpp
+++ b/plugins/single_plugins/expo.cpp
@@ -35,8 +35,23 @@ class wayfire_expo : public wf::plugin_interface_t
         return wf::point_t{x, y};
     }
 
-    wf::activator_callback toggle_cb = [=] (auto)
+    wf::activator_callback toggle_cb = [=] (auto ev)
     {
+        // Avoid self-loop
+        if (ev.source != wf::activator_source_t::PLUGIN)
+        {
+            wf::activator_data_t data;
+            data.source = wf::activator_source_t::PLUGIN;
+
+            for (auto& wo : wf::get_core().output_layout->get_outputs())
+            {
+                if (wo != output) {
+                    wo->call_plugin("expo/toggle", data);
+                }
+            }
+        }
+
         if (!state.active)
         {
             return activate();

[ammen99]

@myfreeweb I took your changes from #828 and put them in the appropriate place. Now you can use an activator binding in caps2esc I think.

The reason to use activator bindings is that there you actually can differentiate what triggered the binding - and modifier and keybinding are separate triggers.

[damianatorrpm]

Also testing this now inse hotspot is merged