Refactor Container class and children

[jcollins-g]

Rename and change semantics for many getters on the Container class.

This makes Dartdoc's use of terminology for class members more closely aligned with Dart and Analyzer internals, and improves separation between the generation layer and Dartdoc internals.

• "Properties" are now called Fields internally outside of the templates themselves.
• Move everything having to do with inheritance to the Class class out of Container.
• Move everything common to all Containers out of Class and into Container and eliminate some duplication.
• Use a consistent naming scheme for template getters in particular:
  • sorted for getters where ordering matters. Don't store and sort lists of items over and over for non-documented ModelElements.
  • staticFields now includes constant static fields, variableStaticFields has the old behavior.
  • instanceMethods and instanceFields for non-statics, rather than methods excluding statics by default.
• Compose getters out of words with consistent meanings, e.g. hasPublicInheritedFields and publicConstantFields rather than using so many abbreviations, so templates are clearer.

Note: this completely breaks markdown generation until the templates are updated. Will add a smoke test for markdown and update those templates in a followup.

[coveralls]

Coverage decreased (-0.04%) to 91.44% when pulling 02b8138 on nnbd-pre-cleanup into 1196ef0 on master.

[jdkoren]

@jcollins-g There are a lot of additions under testing/test_package_custom_templates/templates. That directory really only exists to check that running with the --templates-dir option works; IMO those templates don't need to exercise all the features or access all the template-able members, and I didn't intially intend for them to do that since since other tests will. Is there a reason you feel those additions are necessary?

Will do another pass on the rest a bit later.

[jcollins-g]

I didn't want to hand-edit all the templates so I just copied the whole directory across for the templates-dir test, modifying only the index so it's possible to tell the difference by examining the output (and therefore verifying that dartdoc is using the right template dir).

There is probably a better way to do this, open to better ideas.

[srawlins]

Renaming and reorganization looks good.

Full disclosure I did not thoroughly review HTML / markdown templates; just scanned.

[srawlins]

Hmm, does the toList here add anything important?

[jcollins-g]

I don't think so. Removed.

[srawlins]

Hmm, should we just use spread here? Does quiver.concat buy us something in a getter?

[jcollins-g]

quiver.concat allows for lazy evaluation. Perhaps that is unimportant compared to the clarity of the spread operator, though....

[jdkoren]

I didn't want to hand-edit all the templates so I just copied the whole directory across for the templates-dir test, modifying only the index so it's possible to tell the difference by examining the output (and therefore verifying that dartdoc is using the right template dir).

Checking the index afterward for a specific string seems reasonable.

I did sort of like that the template directories were quite different as it ensures that we don't inadvertently rely on specific filenames or directory structure (aside from what's documented in the help string). Not sure how strongly I feel about it, though.

[jcollins-g]

@jdkoren I hear you on not wanting to throw out any coverage we might have been getting there. However, code coverage results suggests we didn't lose much by changing to a simpler construction, though. Yes, we probably should be testing edge cases in custom templating more effectively. Maybe at some point we can do that with more deliberate intention.