Revert "Revert "#Fixes::158429927::Chaitanya N::Unrestricted file upload in company logo issue is fixed""

This reverts commit ef711ac2.

This reverts commit 23b68adb.

Fixes #723: Dropped few legacy and unused config variables. Retained those that can be used further.

This makes it possible for the admin to choose their preferred language in the first step of the installer. That choice applies to the rest of the installation process and is set as the default system language in the config file.