Use shorter file names

From looking around standard library packages, I see that filenames are
typically single words only (save for the `_test` prefix and
OS/arch-specific files), so let's follow that style here.

git-svn-id: file:///srv/svn/repo/mai/trunk@4 e410bdd4-646f-c54f-a7ce-fffcc4f439ae

engine.go

@@ -0,0 +1,16 @@
+package simplytranslate_engines
+
+type TranslationResult struct {
+	SourceLanguage Language
+	TranslatedText string
+}
+
+type TranslationEngine interface {
+	InternalName() string
+	DisplayName() string
+	SourceLanguages() ([]Language, error)
+	TargetLanguages() ([]Language, error)
+	Translate(text string, from Language, to Language) (TranslationResult, error)
+	SupportsAutodetect() bool
+	DetectLanguage(text string) (Language, error)
+}