When setting a new value via position object, return an updated position object.
Add several helper functions for position objects & test for them.
Add more position-related methods to multi_type_matrix.
Add several new methods to multi_type_matrix that take position objects.

And write test code for them.
Add performance test on data insertion via position object.
Share element type values where we can.
Add performance measurement test for multi_type_matrix.

Insertion via position object beats the other method hands down.
Adding another case.
Optimize value assignment to a block.

Assigning values to a block in a single step is faster than doing it
one value at a time when the condition permits.
Add new constructor to mtv to support creating instance with array of values.
I think it's better (and safer) to throw here on mis-matching data length.

Better than leaving it alone then causing a hard-to-debug problem down
the road.
Add new constructor to allow initialization of matrix with data array.
Updated.
Update version to 0.9.1 for real.