[Lazarus] New control TLvlGraphControl and new IDE package graph

[Juha Manninen]

This is close to the reverse engineered class diagram tool that was
discussed already a long time ago.
I thought the most difficult part is automatic layout calculation and
this component implements it quite perfectly. Cool!

Still, it cannot be directly used for a class diagram because there
not only nodes connect to each other but a connection can be from a
property inside a node.
It could be extended with special nodes having connection points, and
edges (lines) having graphs at the ends.
At least a diamond and a circle graph is needed for class diagram lines.

Juha