Add package command (#385)

Add package command support: This PR adds package command to CLI. package provides some useful subcommands to use such as packages CRUD and display package detail information. Also it is able to reuse existing package at function creation.

* Check function existence before creating package

* Check package existence

* Add support for downloading archive from given url

The functionality was supported before e238776bf7. Add this functionality back for more flexible usage.

* Add output flag to save archive content in specific file

* Add logs when package create/update

* Fix fnCreate requires environment argument when a pkg is specified

* Fix fnUpdate failed to update function pkg info when a package is specified

* Add package command test

* Fix wrong python test image in test script

* Remove package description fields

* Fix package command not update package but creating a new one

* Set package as pending status only when there is no deploy archive

* Rename function from fetchArchiveFromArbitraryURL to downloadToTempFile

* Use io.Copy to prevent loading all body into memory

* Revise some messages

* Allow user to update package build command

* Allow user to update package content when using function update

* Retrieve pkgName from function packageref if it’s not specified

* Fix function failed to update due to resource conflict

* Fix test case failure due to single quote

* kick ci

* Fix failed to update function packageRef

* kick ci

* kick ci

environments/fetcher/fetcher.go

@@ -78,12 +78,15 @@ func downloadUrl(url string, localPath string) error {
 	}
 	defer resp.Body.Close()
 
-	body, err := ioutil.ReadAll(resp.Body)
+	w, err := os.Create(localPath)
 	if err != nil {
 		return err
 	}
-
-	err = ioutil.WriteFile(localPath, body, 0600)
+	_, err = io.Copy(w, resp.Body)
+	if err != nil {
+		return err
+	}
+	err = os.Chmod(localPath, 0600)
 	if err != nil {
 		return err
 	}