Unbox Variant and Maybe at first

These special types should be unboxed first, because they might be also
interpreted as other types causing bugs, e.g. string type boxed in
Variant has been converted to JavaScript object type instead of string
type.

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Add null window object in bare JavaScript env

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Add Nuvola.warn to JS API

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Improve console.log and friends fallbacks

Issue warning, convert arguments to string and join them.

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Split main.js to logging and fallback

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>