Improve node and game variation editing

Some ideas of the options that could be offered to the user for editing nodes and game variations. A popup menu with all the entries described below would probably be too long on smaller devices.

Create new setup / annotation / markup nodes

Long-press on a node in the node tree view => Displays a popup menu with the following entries:

Condition                                             Menu entry                               Action when selected
-------------------------------------------------------------------------------------------------------------------
If not root node                                      Insert node                              New parent node
If no branching node                                  Add node                                 New first child
If no branching && first child exists                 Add variation                            New last child
If branching node                                     Add variation before current variation
If branching node                                     Add variation after current variation
If branching node && current variation is the first   Add variation at top
If branching node && current variation is the last    Add variation at bottom

Move existing setup / annotation / markup nodes

Use drag & drop.
Annotation and markup nodes can be moved from anywhere / to anywhere, because they don't influence the board state.
Setup nodes can only be moved to a location before the first move.
- If there are moves after the old location: TODO
- If there are moves after the new location: TODO
- If there are setup nodes after the new location => The first such setup node must be adjusted so that the net result of the move is the same board state.
- Ditto if there are setup nodes after the old location.

Move existing variations

Long-press on a child node of a branching node in the node tree view => Displays a popup menu with the following entries:

Move variation one up (unless the variation is already at the top)
Move variation one down (unless the variation is already at the bottom)
Move variation to top (unless the variation is already at the top)
Move variation to bottom (unless the variation is already at the bottom)

Delete existing nodes and variations

Long-press on a node in the node tree view => Displays a popup menu with the following entries:

Condition                 Menu option
----------------------------------------------------------
If root node              -
If child node exists      Discard node and all child nodes
If no child node exists   Discard node

Edit existing nodes

Long-press on a node in the node tree view => Displays a popup menu with the following entries:

Condition                  Menu option
----------------------------------------------------
If annotations exist       Delete annotations
if markup exists           Delete markup
If setup exists            Delete setup
If multiple things exist   Delete all (except moves)

herzbube / littlego