netperf v0.4

• Allow extra influxdb tags in label
• Update serial parsing to work for 5g_nsa
• Use LTE parameters for 5GNSA since they don't match the datasheet
• Don't use test id if there's only one test
• Add retry for reading serial port
• Remove tags from main label
• Report network mode as a tag instead of a field
• Add -w option to wait between tests
• Include timestamp in influxdb data points
• Save labels to filename