update path of select2.png to be correct

It seems that our asset pipeline things confuse connect2 so we need to
hardcode the path of the select2 down arrow so it works

Fixes #503 and Fixes #642
Add in poplus logo, link and 'a poplus component' to the footer

Fixes #447
Only show copy API endpoint button if Flash is working

If flash isn't present/working then clicking on the button silently
fails so hide the button by default and only show it if flash is
available.

Fixes #622