Add JSONB config for useBigIntegerStringAdapter and useBigDecimalStri…

[jgallimore]

…ngAdapter

Following on from #134, could this change be considered?

This should allow this:

final JsonbConfig config = new JsonbConfig().withPropertyNamingStrategy(PropertyNamingStrategy.IDENTITY)
          .setProperty("johnzon.useBigIntegerStringAdapter", "false")
          .setProperty("johnzon.useBigDecimalStringAdapter", "false")
          ;

(backport of #136)

[jeanouii]

For consistency, do you mind using the same code block than in the main branch so future user upgrades will still work.