Dynamic BoxAuthentication lauout

Please remove resources used in BoxAuthentication. This will allow using this library in other apps as a compiled .jar file, not as source-based library.

This can be done easily:

``` java
@Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

mApiKey = getIntent().getStringExtra("API_KEY").trim();
if (mApiKey == null || mApiKey.length() == 0) {
setResult(AUTH_RESULT_FAIL);
finish();
return;
}

// setContentView(R.layout.box_authentication);

FrameLayout layout = new FrameLayout(this);
layout.setLayoutParams(new ViewGroup.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
mLoginWebView = new WebView(this);
mLoginWebView.setLayoutParams(new FrameLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
layout.addView(mLoginWebView);
setContentView(layout);
...
}
```

Locate BoxAuthentication and the box_authentication layout resource, then inspect how the authentication screen is created. Confirm which resources are used only by BoxAuthentication and replace that dependency with the programmatic layout described in the issue. Done means the SDK can be consumed as a compiled .jar without those resources.

Written by the indexing model from the issue text.