Bug 5845: can not transform ba to bi, when keys contain boolean type

Bug 5845: can not transform ba to bi, when keys contain boolean type

Reworked check for getter methods, added test method
for getting boolean key starts with is due to the fact
that it is a boolean.

As it turns out, LeafNodeCodecContext already gives us
a ready-made name via getGetter().getName(), so let's
use that.

Also take a moment to do some minor cleaups while we're
at it.

Change-Id: I36adc6ff37159dba257a6fa437ab55eb49ed1151
Signed-off-by: Filip Gregor <fgregor@cisco.com>
Signed-off-by: Robert Varga <rovarga@cisco.com>