Make footerText configurable

[jplahti]

Could the localization footerText be changed into configurable "This service provided by XXX", where XXX comes from ENV, with optional link url for the name of the provider?

[julianq]

Second this. Would like option to provide text as link to URL, text without link to URL, and no text. Cannot figure out how to edit that, either within the locale files or hide it with CSS.

[timvisee]

Implemented in #103