Module specific lensnaming

[zenna]

Currently lensnames effectively have global scope. This may (will) cause conflicts in that one may unintentionally register a filter to a lens from another library.

One work around is for lenses to have scoped within the module.

e.g.

function myf()
   lens(:x,10)
end

The lensname :x would be comverted to :mymodule_x