bumblebee@pdcurtis Update to v3.1.1

[pdcurtis]

Update bumblebee@pdcurtis to version 3.1.1

• Version numbering harmonised with other Cinnamon applets and added to metadata.json so it can show in 'About...'
• icon.png copied back into applet folder so it can show in 'About...'
• Add translation support to applet.js
• Identify strings for translation and remove leading and trailing spaces and replace with separate spaces where required.
• Add po folder to applet
• Create bumblebee.pot using cinnamon-json-makepot --js po/bumblebee.pot
• Version and changes information update in applet.js and changelog.txt
  NOTE: These changes only harmonise the applet with other spices and does not impact the basic applet code which still installs without errors and the menus are as expected. However I have only been able to partially test its actual operation with Bumblebee as I now use Nvidia Prime and Bumblebee is no longer installed on any of my systems. If any issues are reported I will revert this change.