Dark mode fixes and minor project updates

[undecoded-coder]

Dark mode fixes, asset updates and migration to asset catalog, and other minor changes.

At a glance:

• Bumped minimum deployment target for AMSProgressBar and LSynth to 10.11
• Replace call to deprecated -beginSheet in AMSProgressBar
• Dark Mode fixes
  • Removed custom scope bar and status bar backgrounds
  • Changed color preference defaults to use appropriate system colors by default
  • Fixed donation dialog background color
  • Fixed empty inspector text label color
  • Fixed file outline row background color
  • New placard button icons
  • New document, line and conditional line icons in file outline
• Migrated image assets to asset catalog

[Updated PR description]

[undecoded-coder]

@allenmonroesmith if there's anything I could do to help this project along let me know! Thanks!

[allenmonroesmith]

Please make PRs for any other fixes and improvements you have made.

From a technical perspective, the most critical issues are:

• Need to enable ARC
• Need to migrate away from OpenGL—I can only hope Ben has some clue how to tackle that, as I don't
• Heaven only knows what's happened with LDraw over the last 8 years

[undecoded-coder]

Please let me know if the application is releasable with dark mode right now.

I'll look through some of the auxiliary windows just to make sure, but so far (with these changes) it's been fine. The only thing I have yet to solve is a slight change between window and row background color in the file outline (Edit: this was due to the text field cell drawing its own background via the checkbox in Interface Builder; on a separate note, I may try converting this to be view-based instead of cell based at some point).

[undecoded-coder]

Minor text color fix! Beyond that it all looks great now.

The only black-on-dark thing I can find is the icon for line primitives in the file outline. In order to fix that though I think the best thing would be to migrate to using Asset Catalogs (which is orthogonal to this PR).

@allenmonroesmith, I think you'll have to review changes again in order to merge the PR (if everything looks good to you), but I don't know of any other changes to make on this right now, so you can merge it at will.

Edit: I do need to look into the row background color (in Dark Mode) in the outline still.

[undecoded-coder]

That was easy.

[undecoded-coder]

I'll post any other Dark Mode issues on #7 as I find them

[undecoded-coder]

I was hoping to put the asset catalog migration changes into a separate pull request but it didn't turn out that way.

Note: I did not delete the original assets folder yet (though I removed it from the application target) even though it is no longer needed. Let me know if I should, or feel free to do so yourself.

[undecoded-coder]

Okay, I tried adding some new placard icons since the current ones have bright backgrounds.

I could try to just replicate the existing ones without the backgrounds, but I thought I could try these on for size first. That said, it may be better to use alternate images for Dark Mode (now that they are in an asset catalog where you can do that). Let me know what you think!

For comparison, here are some screenshots:

[undecoded-coder]

It says only those with write access to this repository can merge pull requests. So that would be you. :]