15 (Restore a session at startup)

What's Changed

• [Feature] Restore saved windows at startup via D-Bus by @nlpsuge in #39.

  Read How to Restore a session at startup? to learn how to enable and use this feature.

  Please also see this issue #9 for more information about this feature.

• Fix Change the "Are you sure to close open windows ?" to "Confirm ?" ?(#23) by @nlpsuge in #41

Full Changelog: 13...15