Added a lot of minor improvements

[moo24]

• Added support for keyboard
• Added fix in case a image was not loaded correctly (e.g. 404) to automatically load the next image
• Split assignment of content to another function in order to reuse an existing instance with different images later. Helpful on single page web applications
• Other minor code changes

Please check if may changes break any compatibility as my changes are based on 1.4.0 version. I tried to merge them into 1.4.1 without breaking anything.