Improve database import logic handling

[haibol2016]

Hi @apeltzer,

  Are the two 'if' conditions logically problematic? 

https://github.com/apeltzer/fusion-report/blob/master/fusion_report/app.py#L129-L137

       if not params.no_fusiongdb2:
            local_fusions.update(
                {FusionGDB2(params.db_path).name: FusionGDB2(params.db_path).get_all_fusions()}
            )

        if not params.no_mitelman:
            local_fusions.update(
                {MitelmanDB(params.db_path).name: MitelmanDB(params.db_path).get_all_fusions()}
            )
``

[apeltzer]

I see your point - maybe not optimal but it doesnt cause trouble, reading these two files is also not expensive operation and I didnt want to change the entire approach so far. Maybe I'll do a logical fix in one of the next releases, so that this is becoming less cumbersome to read.