Open fixes after 2.0

[sstroemer]

Updated list of open points to fix/clarify after discussion on 12.11., in addition to all points in this comment:

todos:

• virtuals without functions do not get their parameters (see parse.jl Line 65)
• replace meta.parse in templates by JuliaSyntax
• implement "validate: my_valid.jl" instead of writing code in strings
• check/fix that "tag vererbung" does not work for container templates (bess is no householde)
• document that addons should now return true/false
• document the weird regex in _string_to_fevalexpr
• update the "breaking changes" list
• compile a "new features" list
• create a "how to update to 2.0" list
• Fix documentation of core components being part of the Python docs

notes:

• document tags (and their casing), including auto-tagging feature

test:

• loaded module in main that has dependency that IESopt does not have (timezones.jl)