Make LayoutManager compatible with Terminator 1.90 (gtk-3)

[dmirtillo]

Hi,
as terminator 1.9 is being pushed as stable in the official arch repo ( https://www.archlinux.org/packages/community/any/terminator/ ), the LayoutManager plugin is no longer working.
The error is the following:
PluginRegistry::load_plugins: Importing plugin LayoutManager.py failed: When using gi.repository you must not import static modules like "gobject". Please change all occurrences of "import gobject" to "from gi.repository import GObject". See: https://bugzilla.gnome.org/show_bug.cgi?id=709183

[microdou]

PR.