Fixes for nG6:

• Path to application.prperties fixed in nG6_utils.php (Issue #216)
• Fix for the purge delay variable in nG6_pi6_purge.php (Issue #217)
• .png files are now displayed in the analysis page (Issue #218)
• Update to workflows/components/contaminationsearch.py (Issue #221)
• Remove the size display from the project an run pages (Issue #224)
• Remove the hidden runs and analyses from the purge process (Issue #225)