[analyzer] ProgramPoint: more explicit printJson()

Summary: Now we print out every possible kinds of ProgramPoints.

Reviewers: NoQ, xazax.hun, ravikandhadai, baloghadamsoftware, Szelethus

Reviewed By: NoQ

Subscribers: szepet, rnkovacs, a.sidorin, mikhail.ramalho, donat.nagy,
             dkrupp, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D62946

llvm-svn: 363187