Add support for "name:type" style Headers

Currently use of Header row (and manual construction of `CsvSchema`) assume that headers only specify name of column position. But there exists usage, wherein header line contain type mappings too:

```
name:string,enabled:boolean, ...
```

It would be great to support this.

There is an immediate problem with "type" definition: as things are, only a very limited set of types is recognized for `CsvColumn`. But we could divide implementation into two main parts:

1. Support mapping to existing small set of types (probably allowing case-insensitive type definition)
2. Support configurability of extension types, by providing converters from `String` value into target types.

For (2) there is also additional step needed: whereas we could expose `JsonToken` values for:

1. Strings
2. Numbers
3. Booleans
4. nulls

everything else would need to be exposed as `JsonToken.VALUE_EMBEDDED_OBJECT`.
But if so, any and all types could be supported -- as long as `jackson-databind` deserializers (`JsonDeserializer` impelmentations) consider possibility of embedded type.

Doing above is not trivial, but would be a very powerful mechanism for customized binding from CSV data. Some amount of duplication would likely result (for Converters) but that seems acceptable.