Provide embedding manager (#16)

* Provide the Embedding management UI

* Update Fastembed documentation

* Add validation when adding / updating embeddings

* Stop using the old ktem embeddings manager

* Set default local embedding models

* Move the local embeddings below in flowsettings

* Update flowsettings

docs/pages/app/customize-flows.md

@@ -193,7 +193,7 @@ information panel.
 You can access users' collections of LLMs and embedding models with:
 
 ```python
-from ktem.components import embeddings
+from ktem.embeddings.manager import embeddings
 from ktem.llms.manager import llms