Add delete administration capability

[dgets]

It's time to add this as more than just a function of the admin panel. People do, after all, make mistakes sometimes.

When #90 is completed, it would be good to add this capability for other users, as well. Perhaps this should come after #90 is implemented.

[dgets]

I think that the way we'll work this view is that without a POST value, we'll display a listing of all administrations for the particular user. They will be in a table, with checkboxes next to them, in order to select them for deletion. Of course there will be a select all option, as well, as the number of administrations may be huge.

There will also be a field (probably a drop-down selection) that will allow filtering of those results per-substance. If the POST value contains a hidden field value that is sent along with that particular separate form, then the views.py code will only display that particular substance's entries for the user.

Finally, of course, if any administrations or select all is checked, the following administrations will be confirmed for deletion and wiped from the database. A hidden field value may be used to determine this as well, though checking for null values within certain form elements may be possible, as well.

Upon addition of user groups (#90), this will be available for other users, as well as just the currently logged in one.