Fix Buildinfo generation (bug 2252)

In previous releases, json string for buildinfo was partially generated at compile time and rest of the json string (portion of info which can be obtained only during runtime) was appended at run-time(json parsing was not done). The partially generated json string was not a fully validjson string.

Now, the json string generated during compile time is a fully valid json string. The Run-time buildinfo is added to this json string by parsing the compile-time generated buildinfo. (Added json parser to parse buildinfo and add additional key-value pairs)

Also removed unused API from misc_utils.cc