Initial multiple repository support

And lots of code reshuffling which likely should've been done in
separate commits..

package_manager/bpkg/__init__.py

@@ -1,18 +1,19 @@
-import logging
+__all__ = (
+    "exceptions",
+    "types",
+)
 
-log = logging.getLogger(__name__)
+from . types import (
+    Package,
+    Repository,
+    )
+from pathlib import Path
 
-if 'bpy' in locals():
-    import importlib
-
-    log.debug("Reloading %s", __name__)
-    exceptions = importlib.reload(exceptions)
-    Package = importlib.reload(types.Package)
-    Repository = importlib.reload(types.Repository)
-
-else:
-    from . import exceptions
-    from .types import (
-        Package,
-        Repository,
-        )
+def load_repositories(repo_storage_path: Path) -> list:
+    repositories = []
+    for repofile in repo_storage_path.glob('*.json'):
+        # try
+        repo = Repository.from_file(repofile)
+        # except
+        repositories.append(repo)
+    return repositories