Added Functionality to delete Entities

[mapthegod]

deleteEntity()

Added

Aura\Marshal\Type\GenericType->deleteEntity($identity_value)

The Function takes the identity_value of the Entity to be deleted as parameter and deletes it from all indicies.

getDeletedEntitiesIds()

Added

Aura\Marshal\Type\GenericType->getDeletedEntitiesIds()

The function takes no arguments and returns an array of identity_values of Entities deleted using deleteEntity()

Tests

Added several test for the Deletion Functionality

[harikt]

May I know why you need delete Entities?

[mapthegod]

@harikt I'm working on a DataProvider which automatically handles saving new, updated and now also deleted Entities to a backend. And as I need to have a delete functionality on some of the Entites, I wrote these little functions.
I just decided to open a pull request to share it with you, and discuss whether it should be merged into the main repo or not.

[mapthegod]

We may also discuss this in the IRC, if you wish

[harikt]

@mapthegod Thank you for the quick response. I was just curious to know, that's all. Please wait for @pmjones to look into it further . I am not that much into Marshal :) .