2-add-keyword-support (#6)

More development.

More types.
Fixed attribute groups in requests.
Started on client.
Saving data to file.

More types. Printing from chromeos works a little bit.

More types.

Spelling corrections.

WIP: Fix keyword handling

Move request to a separate file and add test.

Co-authored-by: Henrik Sölver <henrik.solver@gmail.com>
Reviewed-on: #6
Co-Authored-By: henrik <henrik.solver@gmail.com>
Co-Committed-By: henrik <henrik.solver@gmail.com>

packages/ipp/naturallanguage.go

@@ -0,0 +1,43 @@
+package ipp
+
+import (
+	"io"
+)
+
+type naturalLanguage struct {
+	name  string
+	value string
+}
+
+func NewNaturalLanguage(name, value string) *naturalLanguage {
+	c := new(naturalLanguage)
+	c.name = name
+	c.value = value
+	return c
+}
+
+func (c naturalLanguage) String() string {
+	return c.name + ":" + c.value
+}
+func (c *naturalLanguage) valueTag() tag {
+	return naturalLanguageValueTag
+}
+
+func (c *naturalLanguage) unmarshal(byteStream io.Reader) {
+	c.name, c.value = unmarshalSingleValue(byteStream)
+}
+
+func (c *naturalLanguage) marshal() []byte {
+	l := 5 + len(c.name) + len(c.value)
+	b := make([]byte, l, l)
+	b[0] = byte(naturalLanguageValueTag)
+	marshalNameValue(c.name, c.value, b[1:])
+	return b
+}
+
+func (c *naturalLanguage) size() int {
+	l := 1 + 4 // The attribute tag + 2 lengths
+	l += len(c.name)
+	l += len(c.value)
+	return l
+}