Option Types

Recently @doitmax brought the [OptionTree-Custom-Option-Types](https://github.com/doitmax/OptionTree-Custom-Option-Types) repository he created to my attention, so I've created a new branch to work on merging those new option types into the core. These first six will be added into the 2.5.0 release, with the possibility more may be added if time permits.

- [ ] Border
- [ ] Box Shadow
- [ ] Color Opacity
- [ ] Dimension
- [ ] Link Color
- [ ] Spacing