NEXXT 3.4 released

This version comes with a focus on improving working with maps, as well as metasprites. There's also a new tool to help build for accessibility!

First, a ratification - the attached release notes in the zip had a few mistakes:
-"Swirl move" on metasprites is [Ctrl+Alt+Right mouse drag]
-"Mirror move" on metasprites is [Ctrl+Shift+Right mouse drag]

Here's a summary of the new and changed things:

- Crop canvas [Alt+C,C]
- Alignment controls added to Set Canvas Size [Ctrl+Alt+N]
- Cut (ctrl+x) on Canvas now also cuts attribute data, so long as the whole attribute cell is within the selection
- Navigator [F6]  now renders 400% faster when zoomed out
- Colour Perception Testing Filters [Ctrl+Shift+F2] is a new tool that lets you spot potential contrast- or distraction issues for different types of colour perception. It's not an accurate simulation of said vision types, but can assist in giving you a clue what to watch out for.  
-Metasprite canvases on the Metasprite Tab [F2] and Metasprite Manager/Animator has increased size from 128 to 144 NES pixels. 
This makes them a bit more ergonomic to work with, and especially helps a bit when zooming in on the Animator. 
-GUI elements for the Metasprite Tab and Metasprite Manager/Animator have been subtly rearranged for better usage of the given screen space.
-You can now multi-select sprites directly on the Metasprite canvas, without having to resort to selecting from the list. 
-You can also multi-move sprites
-In addition, there are two special multi-moves: mirror-move, which moves sprites together or apart in a mirrored fashion, and swirl move, which moves sprites together or apart in a swirly fashion. Both are handy for FX animations. 
-A new context menu button on the Metasprite tab lets you toggle axis of the "mirror move". More features are planned to be added to this context menu in the future. 
-The "constant playback rate" mode for the Animator now has a context menu to help fine tune the rate. 
This is useful for when wanting to analyze an animation free from the context of intended durations. 

Bugfixes:
-Broken metasprite as image export fixed
-Save session didn't store loop tags (and other tags) correctly. fixed.
-Scrolling the metasprite list in the Manager/Animator also affected zoom level. Fixed.
- Loading a new session didn't flush out old metasprite labels. Fixed.
-"Insert new metasprite" had no handling for certain metadata like tags. Fixed.