KDTree functions for KDTreeType

[paradoxysm]

Describe the bug

Since KDTree.insert only checks the value's 'axis', any override types don't exactly follow.

To Reproduce

Steps to reproduce the behavior:

1. Create a class that extends KDTreeType and has two values, one which __getitem__ looks at.
2. Insert two instances of this class where said value is equal but the objects are not equivalent.
3. The tree will only insert the first object.

Expected behavior

KDTree.insert should first check for equality and do nothing if equality is satisfied. One of comparisons on the axis should include when the 'axis' value is equal (I suggest the right subtree).

Desktop (please complete the following information):

• Python: Version independent
• OS: OS independent
• Version: 0.1.5

[paradoxysm]

This extends similarly to search and delete

[paradoxysm]

Resolved for all three methods