Alexander Gemignani plays a dying man with a huge imagination and Heidi Kettenring is his wife in “Big Fish” at the Marriott Theatre through March 19. (Joe Mazza/Brave Lux) The life of a traveling salesman can be an adventure. In the case of Edward Bloom it has included encounters with a Witch, a Giant, and a Mermaid. Or so Edward tells his son Will in “Big Fish,” presented Jan. 25 to March 19 at the Marriott Theatre in Lincolnshire. Performances of the musical by John August (book) and Andrew Lippa (music and lyrics) are 1 p.m. and 7:30 p.m. Wednesdays;...