add the ability to add custom parameter types to the interpreter and mapped macros with any number of macro functions - example added - although it's working it is not ready yet - I have to do some cleanup, doc comments and a TODO

Former-commit-id: 8ac751b649a3b8e59948fd4c89ad53d25f49d0d5

_examples/routing/macros/main.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+
+	"github.com/kataras/iris"
+	"github.com/kataras/iris/context"
+	// "github.com/kataras/iris/core/memstore"
+	"github.com/kataras/iris/hero"
+)
+
+func main() {
+	app := iris.New()
+	app.Logger().SetLevel("debug")
+
+	// Let's see how we can register a custom macro such as ":uint32"  or ":small" for its alias (optionally) for Uint32 types.
+	app.Macros().Register("uint32", "small", false, false, func(paramValue string) bool {
+		_, err := strconv.ParseUint(paramValue, 10, 32)
+		return err == nil
+	}).
+		RegisterFunc("min", func(min uint32) func(string) bool {
+			return func(paramValue string) bool {
+				n, err := strconv.ParseUint(paramValue, 10, 32)
+				if err != nil {
+					return false
+				}
+
+				return uint32(n) >= min
+			}
+		})
+
+		/* TODO:
+		   somehow define one-time how the parameter should be parsed to a particular type (go std or custom)
+		   tip: we can change the original value from string to X using the entry's.ValueRaw
+		*/
+
+	context.ParamResolvers[reflect.Uint32] = func(paramIndex int) interface{} {
+		// return func(store memstore.Store) uint32 {
+		// 	param, _ := store.GetEntryAt(paramIndex)
+		// 	paramValueAsUint32, _ := strconv.ParseUint(param.String(), 10, 32)
+		// 	return uint32(paramValueAsUint32)
+		// }
+		return func(ctx context.Context) uint32 {
+			param := ctx.Params().GetEntryAt(paramIndex)
+			paramValueAsUint32, _ := strconv.ParseUint(param.String(), 10, 32)
+			return uint32(paramValueAsUint32)
+		}
+	}
+	//
+
+	app.Get("/test_uint32/{myparam:uint32 min(10)}", hero.Handler(func(paramValue uint32) string {
+		return fmt.Sprintf("Value of the parameter is: %d\n", paramValue)
+	}))
+
+	app.Get("test_uint64/{myparam:uint64}", handler)
+
+	app.Run(iris.Addr(":8080"))
+}
+
+func handler(ctx context.Context) {
+	ctx.Writef("Value of the parameter is: %s\n", ctx.Params().Get("myparam"))
+}