acl: refactor the package

This commit:

  * replaces the wrappers of the messages to eacl sub-package;

  * renames Target to Group in eacl package;

  * defines Group constants;

  * replaces EACLTable message marshaler (unmarshaler) with custom MarshalTable
    (UnmarshalTable) of the Table.

acl/extended/types.go

@@ -0,0 +1,73 @@
+package eacl
+
+// OperationType is an enumeration of operation types for extended ACL.
+type OperationType uint32
+
+// HeaderType is an enumeration of header types for extended ACL.
+type HeaderType uint32
+
+// MatchType is an enumeration of match types for extended ACL.
+type MatchType uint32
+
+// Action is an enumeration of extended ACL actions.
+type Action uint32
+
+// Group is an enumeration of access groups.
+type Group uint32
+
+// Header is an interface of string key-value pair,
+type Header interface {
+	// Must return string identifier of header.
+	Name() string
+
+	// Must return string value of header.
+	Value() string
+}
+
+// TypedHeader is an interface of Header and HeaderType pair.
+type TypedHeader interface {
+	Header
+
+	// Must return type of filtered header.
+	HeaderType() HeaderType
+}
+
+// HeaderFilter is an interface of grouped information about filtered header.
+type HeaderFilter interface {
+	// Must return match type of filter.
+	MatchType() MatchType
+
+	TypedHeader
+}
+
+// Target is an interface of grouped information about extended ACL rule target.
+type Target interface {
+	// Must return ACL target type.
+	Group() Group
+
+	// Must return public key list of ACL targets.
+	KeyList() [][]byte
+}
+
+// Record is an interface of record of extended ACL rule table.
+type Record interface {
+	// Must return operation type of extended ACL rule.
+	OperationType() OperationType
+
+	// Must return list of header filters of extended ACL rule.
+	HeaderFilters() []HeaderFilter
+
+	// Must return target list of extended ACL rule.
+	TargetList() []Target
+
+	// Must return action of extended ACL rule.
+	Action() Action
+}
+
+// Table is an interface of extended ACL table.
+type Table interface {
+	// Must return list of extended ACL rules.
+	Records() []Record
+}
+
+