moved pdbe code to extensions folder

src/apps/viewer/index.ts

src/examples/basic-wrapper/index.ts

src/extensions/pdbe/index.ts

src/extensions/pdbe/preferred-assembly.ts

src/extensions/pdbe/struct-ref-domain.ts

src/extensions/pdbe/structure-quality-report/behavior.ts

src/extensions/pdbe/structure-quality-report/color.ts

src/extensions/pdbe/structure-quality-report/prop.ts

src/mol-plugin/behavior/dynamic/custom-props.ts

src/mol-plugin/index.ts

src/perf-tests/mol-script.ts

src/servers/model/properties/providers/pdbe.ts