Added Tool\CrossIndex class

[webdevsHub]

Implementation of #830, #473, #829, #836.

In unreleased https://github.com/ruflin/Elastica/blob/reindex-refactoring-to-copy/lib/Elastica/Util.php#L199 branch reindex/copy was added to Elastica\Util class. It does not belong there in my opinion if you look at the other functions in that class. So I created a new Tool namespace.

That namespace can be used by #840 as well (or any other future tools).

[ruflin]

@webdevsHub Can you briefly elaborate on what belongs into Util and what into the Tool namespace? We should document this somewhere so we can use it for future features to decide where they belong. The part I don't like too much is that we have a class with only static functions. It feels a little bit "wrong" :-)

[webdevsHub]

Naming is inspired by Doctrine. Utility is a collection of things you need for internal Elastica coding and Tool for complex functionality for lib users (in Doctrine it is Pagination and the console commands). Do you have any other ideas for a good naming?

I used static like in Util because there is no state and therefore no need to create an Instance

$crossIndex = new CrossIndex();
$crossIndex->reindex(/*...*/);

=> more code overhead as

CrossIndex::reindex(/*...*/);

[ruflin]

I added a note here and merged your pull request. 288a1ec

[webdevsHub]

stooop :) changelog missing

[webdevsHub]

I am going to add it immediately

[ruflin]

Missed that one. Sorry.