TSV base encoder

[skipor]

const debugChecks = tag.Debug // On true, checks fields order, types, and constraints (string has no whitespaces for example)
type FildType int
const (
    IntType FieldType = iota
    Float32Type 
    Float64Type
    StringType // White spaces are not allowed.
    ...
)
func New(type string, fields []string, fieldTypes []FiledType) *Encoder{}

func (e *Encoder) Start(){}
func (e *Encoder) AddInt(v int64){}
func (e *Encoder) AddString(v string){}
...
func (e *Encoder) Finish(){}

Create such encoder, and use it as base of phout.

By option, which is true by default, in first line print info about file format
{'type': type, 'names': [...], 'dtypes': [...]}
where types are some subset of https://docs.scipy.org/doc/numpy-1.13.0/user/basics.types.html