Another big update

This PR attempts to bring this project more in line with how
the angular-ui team structures their directives.

- Most link logic has been moved to a controller
where it can be unit tested more easily.

- The controller methods are no longer in object notation.

- Added a gridsterConfig constant so a user can specify site wide
gridster configuration

- SetOptions has been changed to "resolveConfig".

- redraw method now toggles the gridster-loaded class and calls updateHeight

- Resolving config now stores the actual values for "width" "colWidth" and "rowHeight" in separate variables of the same name with a "_" prefix. This enables for the retention of the "auto" values which is needed on screen resize.