sysutils/dwatch-json: update to 1.2, restore maintainership

dwatch itself is a powerful modular abstraction layer atop dtrace in
FreeBSD base. This package installs modules that produce JSON instead
of human readable text. This version update adds abstraction services
atop those modules.

Approved by: ler
Reviewed by: ler, woodsb02 (previous revision)
Differential revision: https://reviews.freebsd.org/D36051