Chore: decouple figure class

[cvanelteren]

The figure class is currently doing too many things. Code could be separated more cleanly by adding interface to sub tasks.

Will need to think about how to do this. The changes would need to not yield user facing changes. API must remain the same. Will update this as I get a better overview.

After looking at this for a while. I think these are prime candidates:

• SubplotManager: (standalone, only needs gridspec)
• PanelManager: SubplotManager, gridspec
• SharingManager: LayoutManager (border axes)
• LabelsManager: LayoutManager (coords), SharingManager (share levels)
• LayoutManager: LabelsManager (alignment calls in auto_layout)

The idea is to compose rather to inherent to build building blocks over complex inheriance.