Improve GTFS feed import performance, add messages

- Improve performce by completely disabling the SQLite journal
(not needed, on crash the import can be started again)
- Do not use QTextStream to read GTFS files, read QByteArray lines
directly from QFile, only decode strings
- Do not convert values from string to int/Url/Double in
GeneralTransitFeedDatabase::convertFieldValue(), they get returned
as QVariant and then converted back to int/Url/Double in
GeneralTransitFeedImporter::writeGtfsDataToDatabase()
- Add simple "benchmark" using KDebug::Block, results:
Importing the stop_times.txt CSV-file of the GTFS feed at
http://www.datenfragen.de/openvbb/GTF_VBB_BVG_20110530.zip
into the database went from ~120s to ~70s on my system
(the other files are much smaller, resulting database is ~180MB)
- Add logMessage() signal, provides more information
about the import process
- More information for import job through infoMessage(),
show download speed while downloading and show which table
currently gets imported
- Fix wrongly "const KConfig" to "KConfig" for writing in GTFS service