Rename Intent to IntentBuilder and Inner to Intent

To prepare for upcoming getters to use this crate to *read* incoming
`Intent`s from e.g. `Activity.getIntent()`, the "default" builder
pattern on `Intent` (storing a `Result` inside) is no longer applicable.

Author: MarijnS95

example/src/lib.rs

@@ -1,10 +1,10 @@
 use android_activity::AndroidApp;
-use android_intent::{with_current_env, Action, Extra, Intent};
+use android_intent::{with_current_env, Action, Extra, IntentBuilder};
 
 #[no_mangle]
 fn android_main(_android_app: AndroidApp) {
     with_current_env(|env| {
-        Intent::new(env, Action::Send)
+        IntentBuilder::new(env, Action::Send)
             .with_type("text/plain")
             .with_extra(Extra::Text, "Hello World!")
             .into_chooser()