Feature : add "New Piskel" feature in desktop application

[juliandescottes]

cf #270

Regarding the 'new pisklel' button, I just didn't think a lot about this.
It's easy to integrate in the webapp because I can just open a new tab with a blank sprite.

In the desktop version I guess I could just display a warning if there are unsaved changes, and replace the current sprite with a blank one.

[applesarefum]

You could have a tab system in the desktop app where all of your piskels stay open until you close their tab. It may be tedious to put in, though.

[kult74]

UP this issue/Feature.

Having a warning for unsaved changes might do the job. That's the common way for many software. Tabs can also be useful but maybe a bit complex to setup.

[juliandescottes]

@kult74 There is a warning in the web version, I need to check why this doesn't work in the desktop version.

[juliandescottes]

From #270

Hi, I am not sure but if you open a link on nodewebkit with target _blank I think it will open a new nodewebkit window.

[juliandescottes]

Now implemented for the desktop application