Added Jansson 2.5 JSON library to fillin.

Made Xcode target and makefile for configuring and building libjansson.

Changed template evaluation to look up values in JSON.

Added template_read_json() file.

Removed -e option and added -j/--json and -t/--template options.  Also
allow template and JSON file to be specified as regular arguments at
the end of the command line.

Fixed use after free bug in fillin main() and sitedef main().

Did some header cleanup in base lib.