Merge 'Interface' and 'Core' folders in HBEditor

[Cronza]

Currently, editor code is largely split into the core and interface folders, as a way of separating U.I classes from the functional classes. While this originally worked well, some lines are blurring, and the overall structure is dissolving. We should collapse the two into a single structure

[Cronza]

Folders collapsed, along with the dialogue branch panel U.I files and all input entry widgets