Update and validate Getting Started to support self-serve installations

[tiborauer]

The new website should serve as the first line of support providing as much self-reliance as possible. As a first step, Getting Started should be validated and/or extended.

It is related to the discussion started by @tiborauer in
automaticanalysis/automaticanalysis#229

Tasks:

• Check content for accuracy and validity
• Ensure bug-free examples
• Set up two-tiered examples (tutorial + demonstrations)
• Extend documentation of examples to ensure self-sufficient "getting started"
• (optional) Add automatic data retrieval based on the recently implemented CI

[AljenU]

Also related to discussion automaticanalysis/automaticanalysis#254

[vijayiyer05]

@tiborauer

After discussion with @AljenU, it's noted the following PRs on the code repository start to address the tasks identified above:

• PR #302
• PR #306
• PR #315

Specifically:

• Starter examples using aa/SPM only on Linux have been tested with spot-fixes
• Splitting of examples between tutorials (more basic) & demo has started
• Tutorial examples have been updated with the beginning user in mind
• Updates of data retrieval code for CI, including addition to second tutorial

Hopefully these are useful foundational contributions to help towards your goal of updating the Getting Started website.

One possibility to consider is linking these efforts, via auto-generation of markdown from live scripts. Happy to discuss this further.