Persisted Editor State

[simonbethke]

User story:
As user of SuperSplat I would like to have SuperSplat remembering at least part of the state that it had when I left it the last time.

Details:
At the moment all settings of SuperSplat are just runtime-variables that are lost on exit. With this feature, part of the state of the editor should be stored in window.localStorage to be available when visiting the editor the next time. Properties I would suggest to include for the mvp would be:

• last opened files
• Load all PLY data
• Splat mode
• Splat visibility
• Field of View
• SH Bands
• Splat Centers Size
• Outline Selection
• (don't persist "Show Grid" on purpose)
• Show Bound