commands: Show server error info in browser

The main item in this commit is showing of errors with a file context when running `hugo server`.

This can be turned off: `hugo server --disableBrowserError` (can also be set in `config.toml`).

But to get there, the error handling in Hugo needed a revision. There are some items left TODO for commits soon to follow, most notable errors in content and config files.

Fixes #5284
Fixes #5290
See #5325
See #5324

tpl/fmt/init.go

@@ -22,7 +22,7 @@ const name = "fmt"
 
 func init() {
 	f := func(d *deps.Deps) *internal.TemplateFuncsNamespace {
-		ctx := New()
+		ctx := New(d)
 
 		ns := &internal.TemplateFuncsNamespace{
 			Name:    name,