v0.9.2: Add generated mock packages

Go 1.13 module resolver looks at test packages and will fail if there
are empty packages.

v0.9.1: Add FixType enum

Improves readability of the FixType field of GNSSPVTData.

Output configuration support

Rewrite to support all possible output formats

This rewrite is meant to provide a number of improvements:

* Zero-allocation measurement data reading (using bufio.Scanner)
* Support for all output formats (Float32, FP1220, FP1632, Float64)
* Support for coordinate systems
* Support for programmatic output configuration
* CLI support for output configuration

The test suite relies partly on recorded data with different output
configurations. See `testdata/` for more info.

Reading mesaurements from a pre-configured device now has the API:

~~~go
port, err := serial.OpenPort(&serial.Config{
    Name:     portName,
    Baud:     xsens.DefaultSerialBaudRate,
    Size:     xsens.MinLengthOfMessage,
    StopBits: xsens.DefaultSerialStopBits,
})
if err != nil {
    panic(err)
}
defer func() {
    if err := port.Close(); err != nil {
        panic(err)
    }
}()
if err := port.Flush(); err != nil {
    panic(err)
}
sc := xsens.NewMessageScanner(port)
var d xsens.MeasurementData
for sc.Scan() {
    if sc.Message().Identifier() != xsens.MessageIdentifierMTData2 {
        continue
    }
    if err := d.UnmarshalMTData2(sc.Message()); err != nil {
        panic(err)
    }
    for _, id := range d.DataIdentifiers {
        // handle data type present in message
    }
}
if sc.Err() != nil {
      panic(sc.Err())
}
~~~

v0.8.1

Bump einride/build

v0.8.0

Rename package from xsensgo to xsens

First draft version

Clean up code for proper structure

Much of the code had legacy structure, this is the first commit
for ordering the package