Make array type properties reorderable in inspector

[mysticfall]

Write a custom property drawer or an editor for array/list types that can rearrange/insert/delete items. Currently, items in style definition assets are automatically sorted on update to workaround (i.e. rename an item to the last and resize the list to delete it) this limitation, but it's unintuitive and error prone.

Consider using ReorderableList to implement this feature:

• http://va.lent.in/unity-make-your-lists-functional-with-reorderablelist/