CRUNCH-349 Avoid NPE when logging NPE
CRUNCH-216 Transpose args in MapsideJoinStrategy

Initial move in transposing the parameters for the
MapsideJoinStrategy to bring it in line with other join
strategies (i.e. the left-side table should be the smaller of
the two tables being joined).

Introduce static factory methods for creating MapsideJoinStrategy
instances that load the left-side table into memory, and deprecate
the existing public constructor to warn users of the future change.