#334 File operations on files with non-standard extensions impossible

[Erik Hänel]

File operations with files, which don't have a standard file extension, are not possible. NumeRe will always fall back to the *.dat extension.

Analysis:
This is related to the legacy way of creating valid file paths. There are only a few data extensions, which were valid for NumeRe. This can be solved, by declaring the current file extension as a valid extension.

Implementation:
The fix was implemented as proposed by the analysis. Implementation tests were passed successfully.

Documentation:
The fix was noted in the changes log. Further documentation not needed.

Tests:
The fix was tested manually. No deviation detected. Bug fix implemented successfully.