Parse multiple JSON-format configuration files

- convert from using a single monolithic config file
  to reading multiple files from the directory /etc/pmlog.d
- switch config file format from "ini" to "json"

[GF-4748] pmlogdaemon: Parse multiple config files

Open-webOS-DCO-1.0-Signed-off-by: Hongjeon Ha <hj.ha@lge.com>

Change-Id: Ib5651e4c507782bc607b795606ae097e5e805ab0
Reviewed-on: https://g2g.palm.com/2086
Reviewed-by: Build Verification
Reviewed-by: Hongjeon Ha <hj.ha@lge.com>
Tested-by: Hongjeon Ha <hj.ha@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>