Image uploads (allow size changes)

[kgdunn]

Allow size changes for images. For example

• full width image (700 px width by default): :image:201108/mypicture.png``
• user wants smaller image (500 pixel width): :image:201108/mypicture.png;w500``
• user wants smaller image (300 pixel height): :image:201108/mypicture.png;h300``
• user wants smaller image (40% of max size): :image:201108/mypicture.png;40``

Image will be resized on server.

Images will never be shown with a width greater than 700px (not hard-coded, but specified in settings.py)

[kgdunn]

Done in 193f26c8fee