(Reuters) - Egyptian authorities have detained deposed President Mohamed Mursi for 15 days over an array of accusations, including killing soldiers and conspiring with the Palestinian group Hamas, the state news agency said on Friday. The report came just hours before millions of Egyptians were expected to take to the streets in mass rallies for and against Egypt's first freely elected leader, who was ousted by the military on July 3. Friday's step provided legal grounds for the continued detention of Mursi, who has been held by the military since he was ousted. The charges relate to his escape, along...