Update welcome/trainer.md, welcome/README.md, SUMMARY.md, pitch/getting-started.md, pitch/slides.md, README.md files

Update welcome/eligibility-and-requirements/README.md, welcome/eligibility-and-requirements/expectations.md, welcome/eligibility-and-requirements/support.md, welcome/training-format/README.md, welcome/training-format/dates-and-times.md, SUMMARY.md, welcome/overview.md files

Deleted welcome-1/eligibility-and-requirements.md, welcome-1/dates-and-times.md, welcome-1/training-format.md, welcome-1/assessment.md, welcome-1/abstract.md, welcome-1/trainer.md, your-virtual-machine/README.md, your-virtual-machine/familiarity-with-the-ubuntu-desktop.md, your-virtual-machine/signing-into-your-virtual-machine.md, accessing-your-data.md, super-user-do.md, pitch/slides.html, the-command-line.md files