Explanation improvements and drained sites warning

[dabercro]

Improvement to workflow view page:

• The errors shown when clicking on an exit code from the workflow details view will only show errors logs from that workflow.
• This will make the regex results more relevant too, since those are now searching only through the workflow's files
• The sites that are in drain are highlighted in red when ACDC is selected. This should make it easier for the operator to know which sites are good ones to submit to.
• Secondary xrootd parameter is added (called just "secondary")