Rename console.crlf() to console.newline(), leaving crlf() as an alias

Also use sbbs_t::newline() as the underlying implementation of
console.newline() rather than a hard-coded CR/LF output loop.

Added new console methods:
	cond_newline() - equivalent of Ctrl-A/
	cond_blankline() - equivlaent of Ctrl-A?
	cond_contline() - equivalent of Ctrl-A\

... so a JS script author doesn't have to output Ctrl-A codes to invoke those
functions.