Add setting of rel notation using GUI and adding keys

[ppalka-lingaro]

Add setting of rel notation using GUI
when adding rel between FK and PK it should add keys to rel, so line will be well connected.
now when I'm dropping line in middle of target column, it's returning error.

how rel are being added now:

dim_store -> fct_session
fct_event_pageview -> fct_session
fct_event_addtocart -> fct_session