Add new read() method that sets read buffer size

[tihomirleka]

New read(UsbReadCallback, int) method added that takes additional parameter which defines size of the read buffer when communicating asynchronously.

[felHR85]

@tihomirleka Thanks for the PR. I will check it out as soon as possible

[subvertallchris]

Think this could be merged and released if it looks good? The 16kb buffer size with callbacks is a showstopper for me. If this isn't releasable, is there a workaround to change the size of the buffer once the callback is set? I looked but didn't see anything.