Support for null (undefined) values in logical binary table columns

[attipaci]

FITS logical columns in binary tables can store true/false values but also undefined (null) values, as the bytes 'T', 'F', and 0 respectively. So far we have not supported the undefined (null) values because we identified logical columns with the Java primitive boolean, which can have only true/false states. (On that note, booleans can be better supported by bit-based columns, see #450).

We should allow creating, setting, and accessing logical columns as the boxed Java Boolean values, which may be null to signify undefined logical values in binary tables.

Thus, addColumn(), setElement(), setColumn() and setRow() may thus accept arrays of Boolean. However, to keep our code backward compatible, getElement(), getRow(), and getColumn()will return values asbooleanarrays. As such we need new methods to access logical column data asBooleanvalues, at least on the element level. (see newBinaryTable.get()` method in #448)