EnhancementHelp wanted
Description
Currently, when you export custom variables in CSV or TSV, you get a file name like: "Piwik Exporter _ _ [start date] - [end date] .csv"
It would be a nice feature to have an extra GET variable to name the file. Example: "downloadName=mySpecialReport" would give: "Piwik Exporter _ mySpecialReport _ [start date] - [end date] .csv"