Wrong behavior of default Array constructor

[meggart]

I do not have a reproducible example at hand, but there is a problem with using the default Array constructor on chunked AbstractDiskArrays. Adding the following method fixed the code:

function Array(a::AbstractDiskArray)
    aout = similar(a)
    aout .= a
    aout
end

but it is worth to investigate and add some unit tests when fixing this.

[meggart]

Duplicate of #37 and #44