Pre-parse all templates

[Abbe98]

Currently, templates are parsed each time they are invoked with include or include_text. This affects the build times of large sites.

To avoid parsing the same file multiple times we should parse them during discovery and store the templates(text & HTML), include or include_text would then just look up the needed template and reuse it each time.

[Abbe98]

Something like the following but somehow without causing circular dependencies:

func DiscoverTemplates() error {
	filepath.Walk("templates", func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if !info.IsDir() && !strings.HasPrefix(path, "templates/layouts") {
			textTemplate, err := text_template.New("").Funcs(function.GetTextQueryFuncs()).Funcs(function.GetTextStringFuncs()).Funcs(function.GetTextMathFuncs()).Funcs(function.GetTextUtilsFuncs()).Funcs(function.GetTextIncludeFuncs()).ParseFiles(path)
			htmlTemplate, err := html_template.New("").Funcs(function.GetHTMLQueryFuncs()).Funcs(function.GetHTMLStringFuncs()).Funcs(function.GetHTMLMathFuncs()).Funcs(function.GetHTMLUtilsFuncs()).Funcs(function.GetHTMLIncludeFuncs()).ParseFiles(path)
			if err != nil {
				return err
			}

			templateCollection := TemplateCollection{
				ParsedTextTemplate: textTemplate,
				ParsedHTMLTemplate: htmlTemplate,
			}
			TemplateIndex[path] = templateCollection
		}
		return nil
	})
	return nil
}