PUBLISHED IN CANADIAN MUSICIAN     Nick Krewen   When it comes to exploring her Celtic ancestry, Loreena McKennitt leaves no stone unturned. She’s trekked to the far corners of the Earth following her muse, this one-woman dynamo on a mission of cultural renaissance. Her travels have taken her to London, Ireland, Athens, Istanbul, Sicily and even a ride on the Trans-Siberian Railway to inspire her latest masterpiece, The Book…