First implementation, probably all wrong.
Doesn't quite compile.
It compiles.
Use Barycentre to simplify transforms.
Cleanup.
Lint.
After eggrobin's review.
Merge.
Merge pull request #274 from pleroy/DOFBarycentre

Add a Barycentre function for DegreesOfFreedom and use it to simplify the transforms.
Fix a typo.
Merge pull request #277 from pleroy/Typo

Fix a typo.
Implement Normalize.
Usages.
After egg's review.
Merge pull request #278 from pleroy/Normalize

Add a Normalize function for Multivectors.
One factory.
Compiles minimally.
Fix the clients.
It compiles.
Lame attempt at having a distinct frame.