Update extract_spectra.py

edited the 'specextract' to work with CIAO 4.6, where it does not take the pbk0 file as an argument anymore
Updated for Ciao 4.6

Specextract in Ciao 4.6 always outputs .arf and .rmf files regardless of whether they are weighted, so the script is edited to check for .rmf and .arf
Merge branch 'patch-2' of https://github.com/martijndevries/Xmaps