Footer jump fixed in both themes

# To test this patch:
1. Fork my repo from here: https://bitbucket.org/yask123/moin-2.0/ 
2. Move to the branch `improvethemes` : `$ hg update improvethemes`
3. Download and apply this patch

Footer jump fixed in both themes
Also:
1. Fixed this issue: https://bitbucket.org/yask123/moin-2.0/issue/6/overlay-issues-afer-reducing-table-width

2. Overridden CSS rules from `common.css` which were interfering with `modernized` theme.
https://bitbucket.org/yask123/moin-2.0/issue/3/css-style-rules-in-commoncss-file