Improve installation reliability

User Story

As a user, I want the installation to be reliable so that I can minimize the risk of wasting time with the setup.

Traceability

• Related to: #
• T-Reqs ID:
• Requirement label: REQ-2.2

Acceptance criteria

• Python path can be manually configured
• pip upgrade shall happen before pip usage
• Automatic tests shall be created to ensure proper behaviour
• treqs installation shall be decoupled from other extension code
• Installation shall check for Python modules first to ensure descriptive errors are always given
• Installation shall work on Windows
  • venv shall be sourced in proper way in Windows
• Extension shows descriptive error if...
  • venv package is missing
  • pip package is missing