Optimize kinds.js module. Add tests

[rustworthy]

• [x] tests and linter show no problems (npm t)
• [x] tests are added/updated for bug fixes and new features
• [x] code is properly formatted (npm run fmt)
• [ ] description of changes is added in CHANGELOG.md // N/A
• [ ] update .d.ts typings // N/A

Changes:

• return early if schema name OR (!) fields not specified when building projection;
• check that 'root' passed to "projection" func respects Schema API;
• add tests for "projection" func;
• treat projection as a private case of 'kindMemory' and simplify 'getKindMetadata' dispatcher func;
• use 'KIND_STORED_DEFAULT_META' and 'KIND_MEMORY_DEFAULT_META' constants to store module defaults;

As a side-note: both 'schema' and 'fields' are words kind of reserved for Schema instance and field attribute of schema instance accordingly, so I would suggest using schemaName and fieldNames where appropriate; not always this is clear from the context.