An overall 75% performance improvement was achieved by refactoring some algorithms.
This also fixes a bug when initializing a UIntX from another UIntX with a different smaller base Element, the base elements on the provided UIntX weren't being packed correctly. Take a look at the new tests added in UIntXInitTests.swift, prior to these changes some tests there would fail.
Finally also renamed UIntX.init(ascendingArray:) to UIntX.init(littleEndianArray:) and included a big endian version as well.