CVS log for loncom/javascriptlib/file_upload.js

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Default branch: MAIN

- Satisfy w3c HTML validation: id attributes must be unique.

- Client-side checking for uploaded file size.
 - File size checks in multi-part problems supported where different size
   limits potentially apply to essayresponse items in the different parts.
 - File size checks supported in essayresponse item(s) in composite pages.

- Prepend LC_ to class name in client-side checking for uploaded file size,
  for purposes of namespacing.

File size checking for uploaded files

A new javascript file, file_upload.js, handles client side file size checking.
The function, checkUploadSize(), accepts an html file input element and a maximum
file size (in bytes) as input.  If the size of the file to be uploaded exceeds the
size allowed, a message is displayed the the element is cleared.  Server side
checking is still used if it passes this test.

Loading file_upload.js adds event handlers to file input elements with
class="flUpload".
    <input type="file" class="flUpload" />

It also looks for a hidden element with id="free_space" that contains the maximum
upload size.
    <input type="hidden" id="free_space" value="$free_space" />

The free space is usually calculated by subtracting a user's disk usage from their
quota allowance.  In some cases it is a fixed value.

I have implemented this for every upload instance I could find.  These include:
* Message attachments
* Authoring space
* Portfolio
* Course editor
* Essay response problems
* Helpdesk request forms
* RSS feed uploads