Migrate old Widget_Defaults container to Gtk::Grid

[Keyikedalube]

Issue description:

1. Gtk::Table to Gtk::Grid
2. Gtk::VBox   to Gtk::Grid

Both Table and Grid has attach() functions but their arguments differ. You've to adapt the existing Table container to Grid by eliminating most of its arguments.

Pen and paper is a good starting point to visualize how each widgets are supposed to be attached :)

[Keyikedalube]

Hacktoberfest is ending soon and I doubt this issue will be resolved at all from new contributors

There are more widgets apart from widget_defaults that use Gtk::Table. Maybe, I could resolve all of them in one PR :)

• widget_coloredit
• widget_waypoint

@rodolforg @ice0 opinion?

[ice0]

I think this is a good idea :)

[Keyikedalube]

I'm working on this :)