WordPress not recognizing theme in /themes/ folder
If you are using a MULTI-SITE installation of Wordpress, you have to first go into Network Admin, select Themes from the left menu and enable the themes you like to use before they can appear on the "Manage Themes" page in the Site Admin section.
Perhaps you are missing a required template file?
At the very minimum, a WordPress Theme consists of two files:
style.css
index.php
On Ubuntu 14.04 you can install the wordpress package simply using sudo apt install wordpress but then you have to set a link to the themes directory.
E.g. for your "newTheme":
ln -s /usr/share/wordpress/wp-content/themes/newTheme /var/lib/wordpress/wp-content/themes