Improve the keymapper

The keymapper, available as one of the options in the starting menu when the EXE is run without a scenery specified, has undergone a few changes:
- Key descriptions are now parsed the way Starter does and are displayed in the window. They are also no longer consumed when saving to a file.
- Unbound keys are now also displayed as well. Not all of them though; some entries won't exist if they are not specified in the eu07_input-keyboard.ini file.
- You can now unbind a key by pressing F10.

The Parser has got a new boolean option: `skipComments`, true by default to leave current behavior unchanged. When set to false, comments will be parsed as ordinary tokens.

editorkeyboardinput.cpp

@@ -25,12 +25,12 @@ void
 editorkeyboard_input::default_bindings() {
 
     m_bindingsetups = {
-        { user_command::moveleft, GLFW_KEY_LEFT },
-        { user_command::moveright, GLFW_KEY_RIGHT },
-        { user_command::moveforward, GLFW_KEY_UP },
-        { user_command::moveback, GLFW_KEY_DOWN },
-        { user_command::moveup, GLFW_KEY_PAGE_UP },
-        { user_command::movedown, GLFW_KEY_PAGE_DOWN },
+        { user_command::moveleft, {GLFW_KEY_LEFT, "Move left"} },
+        { user_command::moveright, {GLFW_KEY_RIGHT, "Move right"} },
+        { user_command::moveforward, {GLFW_KEY_UP, "Move forwards"} },
+        { user_command::moveback, {GLFW_KEY_DOWN, "Move backwards"} },
+        { user_command::moveup, {GLFW_KEY_PAGE_UP, "Move up"} },
+        { user_command::movedown, {GLFW_KEY_PAGE_DOWN, "Move down"} },
     };
 }