add security error handler

It handles, for example, the following error:

```
Error #2044: Unhandled securityError:. text=Error #2048: Security sandbox violation: <ourUrl> cannot load data from https://fbstatic-a.akamaihd.net/rsrc.php/v2/yo/r/UlIqmHJn-SK.gif.
    at path.assets::AssetManager/loadRawAsset()[D:\...\code-shared\src\main\as3\com\path\assets\AssetManager.as:890]
    at path.assets::LoggingAssetManager/loadRawAsset()[D:\...\code-shared\src\main\as3\com\path\assets\LoggingAssetManager.as:86]
    at path.assets::AssetManager/processRawAsset()[D:\...\code-shared\src\main\as3\com\path\assets\AssetManager.as:710]
    at Function/path.assets:AssetManager/loadQueue/path.assets:loadQueueElement()[D:\...\code-shared\src\main\as3\com\path\assets\AssetManager.as:604]
    at Function/path.assets:AssetManager/loadQueue/path.assets:loadNextQueueElement()[D:\...\code-shared\src\main\as3\com\path\assets\AssetManager.as:582]
    at path.assets::AssetManager/loadQueue()[D:\...\code-shared\src\main\as3\com\path\assets\AssetManager.as:569]
```

which causes, that AssetManager never reaches 100%.