[Doc Rework] Create admin.md

[mapedraza]

This PR merge installationguide.md and operations.md into admin.md file.

This PR is part of a bigger series #1329

Note this PR points towards task/doc-rework branch

[fgalan]

Is this removal of the TOC intentional?

[mapedraza]

No, unfortunately was unexpected behaviour of ToC creation plugin used in text editor. Now disabled. A further commit will restore it

[mapedraza]

Restored here: a1cb5da

[fgalan]

Beware the plugins! :D

[fgalan]

Does this section exists in the new document?

[mapedraza]

Yes, in section Logs:

iotagent-node-lib/doc/admin.md

Lines 503 to 524 in 78f0f2c

	## Logs
	This section describes the logs that can be generated by the IoT Agent library. The IoT Agent library uses the following
	log levels:
	| Level | Description |
	| :------ | :-------------------------------------------------------------------------------- |
	| `DEBUG` | Used to log information useful for debugging. |
	| `INFO` | Used to log information about the normal operation of the IoT Agent library. |
	| `ERROR` | Used to log information about errors that may affect the IoT Agent library. |
	| `FATAL` | Used to log information about fatal errors that may affect the IoT Agent library. |
	Additionally, every error log has an associated error code that can be used to identify the error. The error codes are
	composed by a prefix and a number. The following table shows the prefixes used in the IoT Agent library:
	| Prefix | Type of operation |
	| :----------------- | :--------------------------------------------------------- |
	| `MONGODB` | Errors related with the MongoDB repository |
	| `IOTAM` | Errors related with the IoTA Manager |
	| `KEYSTONE` | Errors related with trust token retrieval |
	| `ORION` | Errors in Context Broker access |
	| `VALIDATION-FATAL` | Errors related with management of the Validation templates |

[fgalan]

NTC

[fgalan]

Suggested change

	where `x.y.z` is a particular version of the library (of the ones included [here](https://www.npmjs.com/package/iotagent-node-lib?activeTab=versions))

In addition, the following fragment could be include (I cannot use it in the suggestion due to the usage of ```):

---

As alternative, you can use the master branch as dependency. In this case, you will be using the latest version of the code but note that some instability could exist (as the code in master is work in progress until the next version is closed).

...
"dependencies": {
    "iotagent-node-lib": "https://github.com/telefonicaid/iotagent-node-lib.git#master",
}

[mapedraza]

Done in 6a9bfa0

[fgalan]

LGTM