Fixed False_hp, added Negation_hp and Bool_to_hProp
Removed Bool_to_hProp due to error
added is_true : Bool -> hProp
trailing newlines removed, Negation_hp simplified
Make a notation for trunc_S

This closes #525
Merge pull request #528 from marcbezem/master

Fixed False_hp, added Negation_hp
Merge pull request #532 from JasonGross/trunc-S-notation

Make a notation for trunc_S