Fixed up ArraySourceBlockEnc(Dec)oder:
- fixed some bugs here and there
- changed encSymbolID to esi and srcBlockNum to sbn (much easier on the
eyes!)
- polished here and there
Fixed critical bug!

PaddedByteArray was not taking into account the padding bytes when
bulk writing/reading (it wasn't doing what it was designed to do in the
first place...)
Forced padded enc. symbols and fixed bugs:

Now encoding symbols always have T bytes, even the last source symbol
which includes padding in the buffer. This avoids complex code to check
different lengths when receiving source symbols.

Fixed a very well hidden bug (at least from me). Turns out that when you
wrap an array in a ByteBuffer, you have to be careful if you want the
buffer position to be always 0. You have to slice the array after
wrapping it. Took a while to figure it out.
Fixed bug in generateIntermediateSymbols()
Fixed bugs where K -> Kprime