Add deleteContainer operation

[amine-mejaouel]

This a proposition for adding a new operation : deleteContainer

This includes:

• A usage sample in README.md and Samples project
• A breaking change in the previously named delete operation which is renamed to deleteItem
• Replacement of let execAsync<'T> (op: ContainerOperation<'T>) = ... with method overloading (see static type Cosmos). This is explained by the fact that deleteContainer does not return an AsyncSeq<'t> like all the branches of pattern matches in let execAsync<'T> (op: ContainerOperation<'T>) = ...

[amine-mejaouel]

There is also another commit [add deleteContainerIfExists] that adds a new operation along with all the utilities operation needed to make it work.