Topology comparison via tree display

[westram]

Improve topology comparison features:

1. horizontally mirrored display (#130)
2. colorize species according to their position in a given topology (see below)
3. synchronized scrolling of displays (#683)
4. root synchronization (#449)

---

Colorize species according to their position in a given topology

[blocked by #443]

Calculate topological position for each species according to one given topology (see code added ​here)
Store in species field(?).
Not stored - instead value is calculated on-the-fly and updates on -changes.

Use that topological position to

1. sort another topology (see #445)
2. colorize the display (see use case for #443)