add support for lifted values

[myazinn]

Currently if we want to store things like table name in a variable, we cannot do something like this

val tableName = "my_table"
val id = 1
val query = cql"select id from $tableName where id = $id".as[Int]

We have to do either this

val tableName = "my_table"
val id = 1
val query = (cqlConst"select id from $tableName" ++  cql"where id = $id").as[Int]

Or this

val tableName = "my_table"
val id = 1
val query = (cql"select id from" + tableName ++  cql"where id = $id").as[Int]

This MR adds new syntax for such cases

import unsafe._

val tableName = "my_table"
val id = 1
val query = cql"select id from ${lift(tableName)} where id = $id".as[Int]

Support for it was added for ll three types of string interpolation (cqlConst, cql, cqlt).