Convert test_NCBI_qblast.py to unittest

I also added a html page in Tests/Blast to be used for testing the function
`NCBIWWW._parse_qblast_ref_page`.
I am not testing all cases of this function as I couldn't reproduce the
necessary error pages in NCBI.

Coverage of `NCBIWWW` went up to 78%.
Make each QBLAST test into a test_method