Fixed: viewerWidth/HeightPadding no longer used

-removed viewerHeightPadding and viewerWidthPadding references

-removed a block of code that manually set margins when toggling fullscreen; this was covered by the .diva-outer&.diva-fullscreen LESS rule

Refs #217; not complete as I want to try to simply adjustBrowserDims more if possible and try to remove height/widthProportion vars
Fixed: adjustBrowserDims correctly changes/maintains centre position

Added offset calculations to adjustBrowserDims; if a certain dimension changes size, it will maintain centre position; if it does not change size, it will maintain edge position

Vaguely refs #217
Fixed: reintroducing code for mobile webkit

refs #217