Dynamic-sized n-ary trees

[Pscheidl]

Currently available trees (n-ary, binary) are compile time-sized trees. While useful for computer graphics and gaming engines, offering the benefits of faster allocation, and lower overhead, the usages are limited.

• Growable n-ary tree only, this variant of binary would offer no significant advantages
• Dense tree only (backed by arrays)

[Pscheidl]

Implemented.