First attempt of documentation for Lens
#136 Rename Lens to PLens and SimpleLens to Lens, add more doc to Lens
Merge master in
Update Lens comments
Rename all other Optics using P prefix
Add some docs on Iso methods
merge with master
Add documentation for Iso
Add documentation for Prism
Add doc for the remaining Optics
Merge pull request #148 from julien-truffaut/doc

Rename Optics and add documentation