health: improve MsgPackLite code readability

This commit includes a set of small patches that make MsgPackLite and
SQLMsgPackLite classes more understandable and more performant. These
patches are:

- add a brief javadoc description of the classes;

- add extra comments that enlighten MsgPack binary protocol;

- replace DataOutputStream.write by DataOutputStream.writeByte that
  looks more readable. Another positive effect here is to use a not
  synchronized method that it may improve serialization performance. It
  is ok because MsgPackLite is stateless and can be shared between
  multiple threads as well;

- avoid to use shortened variables names (i.e. os instead of more
  meaningful output, outputStream and so on);

- increase an initial capacity of a map being de-serialized from the
  MsgPack map object (by 25% of the original size). It may help to avoid
  an unnecessary resize operation during the map filling up.

Author: nicktorwald