Refactor loader settings destructuring.
Fix a bug in safeLoad functions.
Exclude c-forbidden content from the plain scalars.

http://www.yaml.org/spec/1.2/spec.html#c-forbidden
Add the anchor/alias readers.
Fix/redesign/complete node composing mechanism.
Add primitive type resolvers.

They are only used for validation when the tag (!!str, !!seq, or !!map)
is explicitly specified.
Add strict mode. (errors instead of warnings)
[tests] Move python-specific samples to the unsupported.
[tests] Move some of the "error" samples to the unsuported.

According to YAML 1.2 specification, these samples are correct.
http://www.yaml.org/spec/1.2/spec.html#ns-uri-char
Add FIXME note to the tag property reader.
[tests] Correct the "error" tests configuration.
[loader] Variable rename: `safeMode` to `validate`.
[loader] Variable rename: `legacyMode` to `legacy`.
Remove deprecated resolver tests.
Remove deprecated parser (*.structure) tests.
Remove deprecated tokenizer tests.
Remove deprecated "canonical" tests.