Added training material

doc/university/README.md

doc/university/training/gitlab_flow.md

doc/university/training/gitlab_flow/feature_branches.png

doc/university/training/gitlab_flow/production_branch.png

doc/university/training/gitlab_flow/release_branches.png

doc/university/training/index.md

doc/university/training/logo.png

doc/university/training/topics/additional_resources.md

doc/university/training/topics/agile_git.md

doc/university/training/topics/bisect.md

doc/university/training/topics/cherry_picking.md

doc/university/training/topics/env_setup.md

doc/university/training/topics/explore_gitlab.md

doc/university/training/topics/feature_branching.md

doc/university/training/topics/getting_started.md

doc/university/training/topics/git_add.md

doc/university/training/topics/git_intro.md

doc/university/training/topics/git_log.md

doc/university/training/topics/gitlab_flow.md

doc/university/training/topics/merge_conflicts.md