add support for hollow tabs

[jsormaz]

Add support for hollow tabs

-Adds a "Hollow Tab" Option
-Formally adds the "Tab label angle" input. This was partially implemented before but was not editable.
-Reworked the tab sketch generation to support these options.

This allows you to put a label on the outside of the bin as well that is visible when the bins are stacked.

[jsormaz]

Man, I'm pretty bad with git. I can't figure out how to remove my changes to "const.py" from this PR.

Those changes should be reverted, they are just my own defaults for my personal bin sizing.

[jensbodal]

Should be able to remove with:

git reset HEAD^ -- const.py
git commit --amend --no-edit

[jsormaz]

Should be able to remove with:

git reset HEAD^ -- const.py
git commit --amend --no-edit

Thanks a lot!
I couldn't get this to work, and I probably made a mess along the way but I got the result by resetting my fork to the upstream and then creating a new commit

I'm going to go read up on git now :)