use PathNotations in statements of uu0

moved path notations from submodule of uu0 to the corresponding constant definitions, thus no need to explicitly import module PathNotations any more to use notations; this commit removes those imports

switched to path notations in statements of hProp and hSet
Merge pull request #35 from benediktahrens/FoundationPathNotations

Introduce some path notations in Foundations, do not use submodules in Foundations