Remove dependency on Gio

[inkeliz]

Currently, all plugins are locked into Gio and on the plugin system usage. In the next month, is expect all plugins to be redesigned (again), to:

Use plugins without op.Ops.
Make it compatible to use without Gio (like on Fyne) or custom window (providing HWID, NSWindow...) directly.

As a result, each plugin will have some folder similar to the following:

xshare - Agnostic of any UI library.
gioshare - Plugin system for Gio.
fyneshare - Widget system for Fyne.

In order words, both will consume xshare behind the scenes. Also, gioshare will provide access to xshare, without the need to use as an operation, so instead of gioshare.TextOp{}, it would be possible to call gioshare.Text() directly. That is useful when the action is already performed outside of the frame.