Moved phenobase references to svlt-pheno; session-persistent phenobase is in its own singleton object

Core tests pass (still iffy on API ones with server), now with core modules in top level svlt.* namespace (no longer need svlt.core.*)

Prototyped namespace package tree: https://packaging.python.org/en/latest/guides/packaging-namespace-packages/

Build config only

See merge request rhodes/model_server!103

Merge staging as release

See merge request rhodes/model_server!102

Dev batch runner stats

See merge request rhodes/model_server!101

Handling of feature extraction on empty RoiSets

See merge request rhodes/model_server!100

Unique stack coordinates in PhenoBase runner client

See merge request rhodes/model_server!99