Better handling of EnergyPlus errors

[shyamamrith]

• The whole process should not stop due to an EP error - this can waste a lot of the user's time. Instead, it would be better to log this error, report it, but continue with the other simulations. The results for the failed BIs can be pushed as "NULL".
• Currently it reports which idf file failed to simulate, and provides a path to this so the user can check the err file. Perhaps it could take the 'last severe error' text from the err file and report this directly in QGIS? These could all be reported in the summary report, see: Generate simulation summary report #33