Containers: added Array::from().

Until now it was not possible to do the following with Array:

    int a[] = new int[3] { 1, 3, 4 };
    Containers::Array<int> b = a; // ?!
Containers: examples of Array usage, minor documentation fixes.
Containers: don't allow Array-to-pointer conversion on rvalues.

Not available in GCC < 4.8.1. Avoids direct-to-segfault code like
this:

    char* a = Containers::Array(5);
    a[3] = 5;