Fix script file issues and move script classes into namespace

[mortenhauberg]

Elastica\Script and Elastica\ScriptFile extends Elastica\AbstractScript.
There are instanceof checks and type-hints for Elastica\Script in different classes.
I've changed the checks and type-hints to Elastica\AbstraceScript, and made Elastica\ScriptFile extend Elastica\Script.

@ruflin suggested to move the scripting classes into a namespace of its own.
We decided to keep the old classes, and have them extend the new classes in Elastica\Script for BC reasons.

Old	New
Elastica\AbstractScript	Elastica\Script\AbstractScript
Elastica\Script	Elastica\Script\Script
Elastica\ScriptFile	Elastica\Script\ScriptFile
Elastica\ScriptFields	Elastica\Script\ScriptFields

Please let me know if anything needs changes :)

[ruflin]

@mortenhauberg Can you update the CHANGELOG.md?

[ruflin]

Can we add a @deprecated message here? Check some other files which are deprecated for some examples.

[ruflin]

LGTM. It would be nice to have at least a deprecated message in the docs in all classes which are deprecated. Here is an example: https://github.com/ruflin/Elastica/blob/f124e598228a6b8a6c249fde6afc07ea7eb1a771/lib/Elastica/Query/Bool.php

[mortenhauberg]

👍
Something like this?

[ruflin]

@mortenhauberg Merged. Thanks. Perhaps in the future we can also trigger an error so it shows up in the logs:

Elastica/lib/Elastica/Query/Bool.php

Line 4 in f124e59

trigger_error('Elastica\Query\Bool is deprecated. Use BoolQuery instead. From PHP7 bool is reserved word and this class will be removed in further Elastica releases', E_USER_DEPRECATED);

[mortenhauberg]

Thank you. I'll create a PR for triggering errors next week :)

[ruflin]

👍