add category management
refactor the page name
add model category
fix the issue when content/name is empty
save it as UTF-8
Move imageHelper out of utils.py
Change default image format back into jpeg

png occupies much more space than jpeg
Do not accept empty news content.
Correct upload dir
Merge branch 'master' of http://git.oschina.net/luohao-brian/phonecms
Cut uploaded image to appropriate size
Merge branch 'master' of http://git.oschina.net/luohao-brian/phonecms
Merge branch 'master' of http://git.oschina.net/luohao-brian/phonecms
Delete original file name after converting it into jpeg