Documentation: add a link to Bear, a tool to help with JSON DB

Patch by Laszlo Nagy


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173949 91177308-0d34-0410-b5e6-96231b3b80d8
Documentation: fix escaping in JSON example


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173950 91177308-0d34-0410-b5e6-96231b3b80d8