Bugfix for Jmeter when all transactions fail

Fixes
* Errors when the failure rate for a transaction is 100%
* Fixes bug where failures of one transaction was assumed to imply failure in other transactions
* Sanitize Transaction Names containing "/" and "?" which led to exceptions and/or failed client charting
thats true, this was a quickfix. The right solution is for us to have a mapping from metric name to sanitized file name that is transparent to the user. If a Jmeter transaction is called "/server/api", our report should show the same and not a sanitized version of it.