BGX reporter/feature importer auto-detection matches any files with at least two sections

[Nicklas Nordborg]

The auto-detection never reaches the stage were the data header regular expression is used. This happens because the standard flat file parser assumes that there is 0 or 1 section only. If the auto-detection parsing ends on an UNKNOWN line the file is not importable, otherwise the file is considered importable. With BGX files the standard auto-detection ends on the second SECTION HEADER and the file is considered importable.

This can easily be tested by creating a file like this:

[SectionA]
[SectionB]

Both the BGX reporter importer and the BGX feature importer will think they can import the file. The solution is to override the isImportable(FlatFileParser) method and continue parsing the BGX file to see if the data header regular expression can be matched.

[Nicklas Nordborg]

(In [1146]) Fixes #239: BGX reporter/feature importer auto-detection matches any files with at least two sections