First split into crockery init and crockery run

The init command creates a crockery.db file containing the domain name and
TLS keypair. The run command starts IMAP and SMTP services based on that file.

Supporting only a single domain is starting to look a bit unnecessary. We'll
see how that goes.

vendor/github.com/asdine/storm/q/fieldmatcher.go

@@ -0,0 +1,39 @@
+package q
+
+import (
+	"errors"
+	"reflect"
+)
+
+// ErrUnknownField is returned when an unknown field is passed.
+var ErrUnknownField = errors.New("unknown field")
+
+type fieldMatcherDelegate struct {
+	FieldMatcher
+	Field string
+}
+
+// NewFieldMatcher creates a Matcher for a given field.
+func NewFieldMatcher(field string, fm FieldMatcher) Matcher {
+	return fieldMatcherDelegate{Field: field, FieldMatcher: fm}
+}
+
+// FieldMatcher can be used in NewFieldMatcher as a simple way to create the
+// most common Matcher: A Matcher that evaluates one field's value.
+// For more complex scenarios, implement the Matcher interface directly.
+type FieldMatcher interface {
+	MatchField(v interface{}) (bool, error)
+}
+
+func (r fieldMatcherDelegate) Match(i interface{}) (bool, error) {
+	v := reflect.Indirect(reflect.ValueOf(i))
+	return r.MatchValue(&v)
+}
+
+func (r fieldMatcherDelegate) MatchValue(v *reflect.Value) (bool, error) {
+	field := v.FieldByName(r.Field)
+	if !field.IsValid() {
+		return false, ErrUnknownField
+	}
+	return r.MatchField(field.Interface())
+}