Instead of having a frame_duration[] array in the Project class. This makes the code much more readable and understandable, using less lines of code and, by avoiding an extra array, we also avoid potential out-of-bound array crashes.
The functionality for the user has not changed, and by testing so far I didn't find any issues.
* Sync for my local files to my repository
* This is frame properties update, it works but I can't be stored while
saving or loading and that makes crashes just the beggining :)
* I forgot this files :P
* Frame Properties update.
* Updating frame properties
* Update Translations.pot
* Changes to CanvasPreview and CelButton change
A Project class contains project-specific data like name, undo_redo, frames, layers, tags and brushes. These variables have been moved from Global. This is the first step towards multiple tab support, where each tab will be a different Project.
The Canvas is now single node, instead of having multiple canvases for each frame. This should also be a performance optimization, since there are less canvas nodes, so there are less _input() calls. It should also fix a rare Undo/Redo issue with motion drawing and making lines. Could be unstable, needs more testing.
As a side effect, the guides are now the same for all frames, so this should also close #246.
Replaces nested Global.animation_tags arrays. Also replaced array.duplicate(true) with looping through the array and creating a new class for each array element, because duplicate(true) does not create new classes, unfortunately, which was causing issues with undo/redo.
