Query-fix in com_content article modal

This change prevents the query from being executed when the value is 0. There is never an article with ID 0 and especially when there are more than one modal select per page, you have several unnecessary queries.
Fixing codestyle
Fixing codestyle
Improving Contact modal field
Improving Categories modal field
Improving Newsfeeds modal field
Code cleanup
Merge branch 'master' of github.com:Hackwar/joomla-cms into patch-1

Conflicts:
	administrator/components/com_categories/models/fields/modal/category.php
Merge pull request #2795 from Hackwar/patch-1

Query-fix in com_content article modal