changed Service.Context to natural representation (map[string]interface{}) from current json encoded string

DEMO:
```
# plu@plu-9: serviced service list
NAME			SERVICEID			INST	IMAGEID				POOL		DSTATE	LAUNCH	DEPID
└─Zenoss.core		km1s0tlq14przd0fv313w8eh	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─opentsdb		1jiuf7m2yax4gut4cqppdm60f	1	.../km1s0tl.../opentsdb		default		0	auto	HBase
  ├─HBase		290dkqdoby2bbu2zitfn35o3o	0					default		0	auto	HBase
  │ ├─RegionServer	1i3qodf20alqc7e8nf13bump4	1	.../km1s0tl.../hbase		default		0	auto	HBase
  │ ├─HMaster		bhup7eagafb0cw2st4hs6cklx	1	.../km1s0tl.../hbase		default		0	auto	HBase
  │ └─ZooKeeper		d6xxx4586zrb7nsfrcglv2bfv	1	.../km1s0tl.../hbase		default		0	auto	HBase
  ├─zeneventd		2ndrw69x431nk41tccon48dbk	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─RabbitMQ		2rdg4ud9jeieslwxbz09a0kc1	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─localhost		3ujh0nds5njxgqc5yg48dpugr	0					default		0	auto	HBase
  │ ├─zenhub		4rj8x7lvzujr5pletv15anc3g	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │ └─localhost		asb9mktaz21iegqgb4e4ecna7	0					default		0	auto	HBase
  │   ├─zenpython	1zjz48p0va95hcv33fr2m6mth	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zencommand	245jbp6hpift1t5hk8pq92mji	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zenjmx		3ytpwiyv8hf6mzr4brpzv1f7h	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zenping		4gi08e28vv08fqrshm611d2eq	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zenperfsnmp	4np1j0zvnz7slz8e5cecuylh4	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zentrap		56yg11tqacn53gfl9iqo1cvmz	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zensyslog	6ukrysgm02295akrc7ggps6xp	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─collectorredis	777jgw2j4jaf2kzc73yv4psjy	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─MetricShipper	9d1wg4ynx091xsz28a56yve3i	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zenstatus	agqu1vg87bw787fhn6ratlu5n	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zenprocess	b4fkeju9d81p1kxtnaxkcywnd	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   ├─zminion		c9p7zoz43lbxxgxx9729v9us9	1	.../km1s0tl.../devimg		default		0	auto	HBase
  │   └─zenmodeler	cpa7nuoiupsdoubjaziibsmo5	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─MetricConsumer	8fziji25znbpcxl9uz3ardx9	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─MySQL		8lvfdqx0q1kgibtmj5va5mr9	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─zenactiond		9kk17nu6saddf1igf28vbjzgh	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─Zope		9q0ip1vmdk63e12ur4biw4aum	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─redis		9rn717b6wtezay5af252cwibv	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─zeneventserver	9y8wky3cn4incc9uo2b3h0e2y	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─zenjobs		dq7aozjlo4uhnubzfcdbsoz7u	1	.../km1s0tl.../devimg		default		0	auto	HBase
  ├─MetricShipper	eimy5hxxovzrbneup0siz0wn8	1	.../km1s0tl.../devimg		default		0	auto	HBase

```