Fix logs in bridgedb.Main to record the filename that was used.
Fix logs in bridgedb.Main to record the filename that was used.

There were a couple loglines in bridgedb.Main, most of them for when the
descriptor files are opened/closed, which did ``os.path.abspath`` on the
filename string taken from the config, and then logged statements like
"Opening something something file: %s" with the absolute path. On the next
line, the non-absolute path of the filename is opened.

 * CHANGE log statements to record paths as they are passed to open().

pagea/bridgedb,wfn/bridgedb,wfn/bridgedb,pagea/bridgedb,mmaker/bridgedb,mmaker/bridgedb