The first collaboration of the theatrical dream team of great American playwright David Henry Hwang (“M. Butterfly,” “Yellow Face,” “Chinglish”) and versatile composer Jeanine Tesori (“Fun Home,” “Shrek the Musical,” “Caroline, or Change”), “Soft Power” is billed as “a play with a musical” with a predominantly Asian American cast. Coming to the Curran in San Francisco, fresh from its world premiere in Los Angeles, it starts as a contemporary comedy and then shifts into a full-blown musical.