share api - remove unneeded attributes

[tomerbsentinel]

Hi,
Please excuse me if I am writing not as per git req. I'm a newbie.

In owncloud.py, line 66-67
`class ShareInfo(object):
"""Share information"""

def __init__(self, share_info):
    self.share_info = {}
    # remove unneeded attributes
    del_attrs = ['item_type', 'item_source', 'file_source', 'parent',
                 'storage', 'mail_send']`

Why did you decide to "drop" the item_type, and item_source or file_source?

My request is to make the folder/file shareable to my group.
From the UI, I can clearly see that the item_source is used:

When you "drop" this data, we can't share it with an internal link.

example for internal link:
https://nc.XYZ.com/index.php/f/7790

From the API response:

My request:

1. Is it possible to return all items and let the end-user choose what he needs?

2. If not all, please remove those from the unneeded:
   'item_type', 'item_source', 'file_source'

3. If possible, I'd like to do this small PR, let me know if I can contribute.

[tobenary]

This PR fixes it.
PR-255