[Doc] Change the term services group to groups

[mapedraza]

Across all the documentation

[mapedraza]

Should the API methods be changed? (in prevision of #752)

iotagent-node-lib/doc/api.md

Lines 1684 to 1751 in c57d892

	#### Retrieve config groups `GET /iot/services`
	List all the config groups for the given `fiware-service` and `fiware-servicepath`. The config groups that match the
	`fiware-servicepath` are returned in any other case.
	_**Request headers**_
	| Header | Optional | Description | Example |
	| -------------------- | -------- | ---------------------------------------------------------------------------------------------- | ---------- |
	| `Fiware-Service` | ✓ | Tenant or service. See subsection [Multi tenancy](#multi-tenancy) for more information. | `acme` |
	| `Fiware-ServicePath` | ✓ | Service path or subservice. See subsection [Service Path](#service-path) for more information. | `/project` |
	_**Response code**_
	- 200 OK if successful, returning a config group body.
	- 400 MISSING_HEADERS if any of the mandatory headers is not present.
	- 500 SERVER ERROR if there was any error not contemplated above.
	_**Response headers**_
	Successful operations return `Content-Type` header with `application/json` value.
	_**Response payload**_
	A JSON object with a services field that contains an array of services that match the request. See the
	[config group datamodel](#service-group-datamodel) for more information.
	Example:
	```json
	{
	"services": [
	{
	"resource": "/deviceTest",
	"apikey": "801230BJKL23Y9090DSFL123HJK09H324HV8732",
	"type": "Light",
	"trust": "8970A9078A803H3BL98PINEQRW8342HBAMS",
	"cbHost": "http://orion:1026",
	"commands": [{ "name": "wheel1", "type": "Wheel" }],
	"attributes": [
	{
	"name": "luminescence",
	"type": "Integer",
	"metadata": {
	"unitCode": { "type": "Text", "value": "CAL" }
	}
	}
	],
	"lazy": [{ "name": "status", "type": "Boolean" }]
	},
	{
	"resource": "/deviceTest2",
	"apikey": "A21323ASDG12312ASDN21LWQEJPO2J123",
	"type": "Switch",
	"trust": "8970A9078A803H3BL98PINEQRW8342HBAMS",
	"cbHost": "http://orion:1026",
	"commands": [{ "name": "on", "type": "order" }],
	"attributes": [
	{
	"name": "swithc_status",
	"type": "boolean"
	}
	]
	}
	]
	}
	```

[fgalan]

Should the API methods be changed?

Maybe that change should be part of PR #1637 (to change code implementation and doc at the same time, when that PR gets merged)

[fgalan]

After merging PR #1635 (and taking into account the deferred task described in previous comment) maybe this issue can be closed.