Added 'DB_File' requirement to some tests files that use it,
so they can be skipped if its missing (ContigSpectrum.t,
SeqFeature.t & transfac_pro.t)
Several LocalDB tests were failing for Windows' ActivePerl,
because ActivePerl were producing a ".index.pag" and ".index.dir"
files instead of a single ".index" file (like Strawberry Perl).
Also, ActivePerl were not deleting temporary files if their
tied-hash was not made undef after the untie on DESTROY,
and had to add several explicit DESTROY calls to test files.