increase max image size (to 5 mb)

[ionous]

client:

• edit.html: now listing the new size and the allowed file types
• addevent.js: changed client handling of http 413 ( returned by nginx ) to be more generic ( the image edit field already has the image size )

server:

• increased nginx limits
• moved node limits and filetypes to config.js,
• changed uploader to better report file type and other image errors

tests:

• added test / images for "too big" and "wrong format"

[onewheelskyward]

Tested in the deploy env, big images came back with an "image too big" message and images under 5mb worked.