Suggestion: Handle Minor versions

[uweschaefer]

It should be possible to handle minor versions without breaking existing code.
The contract for minor versions is, that changes are guaranteed to be downward-compatible.

Facilitating this knowledge, a conversion like this should be possible:

Prereq:

• There is a Transformation registered from 3.1 to 4.0

Scenario a)

Input: message in version 3.2
Requested version: 4.0

• As there is a 3.1->4.0 and a 3.2 can be treated as a 3.1, the transformation should be used.
  The downcast from existing 3.2 to 3.1 will be implicit (without any actual transformation)

Scenario b)

Input: message in version 3.0
Requested version: 4.0

• The upcast from 3.0 to 3.1 will be implicit (without any actual transformation)

Scenario c)

Input: message in version 3.0
Requested version: 5.0

• Transformation needs to fail, as there is no way to get from 4.0 to 5.0, and as it is a major update, it is not guaranteed to be a compatible one.

In General

• If there are more than one possible path through the transformers, the shortest path wins.
• If there are still more than one of equal length, the one that transforms a larger distance earlier, wins - where distance is Decimal of VersionTo - Decimal of VersionFrom (for example 3.2 -> 4.0 = 0.8 distance)