full support for value_int (float values unused) (fixes #2)

btcapi.h
	addition of double sf (standard form) member in currcy_t
	commented members of rates_t
	addition of double buyf, sellf members in rates_t for when btc amounts should not be specified
	int fill_rates() -> bool fill_rates()
	int parse_json() -> bool parse_json()
	const-ified write_data()'s arguments

btcapi.c
	implemented .sf member in currcencies[] array
	added/removed commas in currencies[] array
	cast void *userdata to (char *) in strcpy()

btcutil.c
	edited help() dialogue somewhat

main.c
	implemented integer values (value_int)