WASHINGTON (Reuters) - Democratic presidential front-runner Hillary Clinton on Tuesday released her personal financial disclosure form, covering Jan. 1, 2015, to the present, with a call to Republican Donald Trump to make available his income tax returns.    “The true test for Donald Trump is whether he will adhere to the precedent followed by every presidential candidate in the modern era and make his tax returns available, as Hillary Clinton has done,” spokeswoman Christina Reynolds said in a statement. Clinton’s own disclosure form showed more than $5 million in royalties from her memoir “Hard Choices.” Trump earlier in the day announced that he had filed his personal financial disclosure to the Federal Election Commission on Monday. 