Oil prices remain jittery today as the market digests yet another sanctions-threat targeting Russia. President Trump is said to be mulling new sanctions on Russia’s so-called "shadow fleet" of oil tankers if Moscow doesn't commit to a peace agreement with Ukraine by Friday. Despite many threats, the Trump White House has yet to impose new sanctions on Russia since he took office. Already the Russian economy is incredibly isolated in the West's eyes, while a growing Kremlin reliance on leading BRICS countries such as China and…