New options: specify default box width

- If users specify the value of boxWidth and boxHeight all boxes will
have by default that value (notice that the data-height and data-width
in the image will override the default)
- Changes in demo to show
Random option + improvements

- Added "random" option: the initial picture will be in a random
location (as opposite to the top-left corner from before). Default
value: true. If set to false, it will work as earlier versions.
- Better scoped the settings variable (no longer used as a "global")
- Added new demo page (specific for the defined sizes/positions)
- Updated the minified version
- Renamed the minified version