Base1PluginExecutor should handle reporter-id=0 as null in some cases

[Nicklas Nordborg]

There is a problem with some BASE1 plug-ins when a bioassay set has spots without a reporter (eg the reporter is null). When the BioAssaySetExporter exports data for spots that has a null reporter the column is empty.

Eg.

40076            3752.0    5588.0    47
40077    536225    RP11-381L15    1184.0    2033.0    47

Some BASE1 plug-ins returns the result with a 0 in the corresponding column.

40079    0        6813.3    6835.66    47
40300    233476    RP11-242P12    7000.09    6676.78    47

The proposed solution is to convert the 0 to a null when importing the processed data if:

1. There is no reporter with id=0 in the export. This is probably always true since IDs usually starts at '1'.
2. There was spots data without reporters in the export.

[Nicklas Nordborg]

(In [4631]) Fixes #1167: Base1PluginExecutor should handle reporter-id=0 as null in some cases

Test case converts all empty reporter values to 0.