Made $alert variable more extensible through use of apply_filters() function

This allows the html markup to be altered to developer's liking, as well as the actual alert message text, including CSS class names that need to be modified or added to.
Added else condition to set $first name and $last name to nothing

Fixes 2 Undefined variable notices and "cannot modify header information" warning
Fixed issue with deleting non-complete purchases and having earnings affected. Closes #816
Fixed merge conflict
Updated changelog and version numbers to 1.4.3
[i18n]>update french.po .mo and edd.pot
Merge pull request #818 from fxbenard/master

[i18n] > update french.po.mo and edd.pot
Update assets/js/admin-scripts.js

Update admin-scripts.js to allow for new Media Uploader.
Update includes/admin/downloads/metabox.php

Added blank data attributes, can be modified to control the title and button text of the media uploader: 
data-uploader_title 
data-uploader_button_text
Update includes/admin/downloads/metabox.php

The difference between data-uploader_button_text="Insert" and data-uploader_button_text="" is small but important!
Update includes/admin/downloads/metabox.php

Pippin: Can you go ahead and localize it?
<?php _e( 'Insert', 'edd' ); ?>
me: Stoopid me! yes, think before commit Mike!
Merge pull request #822 from MadeByMike/patch-8

New Media Uploader