Alan Jay Lerner (bookwriter and lyricist) and Frederick Loewe (composer) wrote some of the American theater's most memorable musicals, including My Fair Lady, Camelot, Brigadoon, Paint Your Wagon and Gigi.   Among their most famous songs are ''Almost Like Being in Love,'' ''I Could Have Danced All Night’' and ''Thank Heaven for Little Girls.''  Lerner was born in New York City in 1918 and attended  Choate and Harvard.   Loewe was born in Berlin in 1901 to Viennese parents, made his piano debut with the Berlin Symphony Orchestra at the age of 13 and came to the United States in 1924.   The two met in 1942 at the Lambs Club in New York City when Loewe approached Lerner about collaborating on a show.  In 1947, they had their first Broadway hit, Brigadoon, followed in 1951 by a second success with Paint Your Wagon which included such songs as "They Call The Wind Maria," "I Talk to the Trees" and "Wand’rin' Star."   In 1956, My Fair Lady, with Rex Harrison and Julie Andrews, opened on Broadway.   Often called the "perfect musical," the show ran for 2,717 performances and the cast album sold more than five million copies.  Their 1958 film musical, Gigi, won nine Academy awards and, in 1960, came the last great success of their partnership, Camelot, starring Richard Burton and Julie Andrews.  In 1974, Lerner lured Loewe out of retirement to work on their last venture together:  a film version of Antoine de St Exupéry's The Little Prince.  Lerner went on to collaborate with other composers including Burton Lane, Leonard Bernstein and Andre Previn. He died in 1986 at the age of 67.   Loewe died two years later at the age of 86.