wildcard functionality in API

when filtering partial values, SlashDB 0.9.23 has an ability to replace the default "*" wildcard value using an additional query parameter - this should be reflected in our Angular SDK api
`
https://beta.slashdb.com/db/Chinook/Invoice/BillingAddress/* Street.json
`
can become
`
https://beta.slashdb.com/db/Chinook/Invoice/BillingAddress/$ Street.json?wildcard=$
`