已知圆\(C\):\(x^{2}+(y-4)^{2}=4\),直线\(l\):\((3m+1)x+(1-m)y-4=0\)
\((\)Ⅰ\()\)求直线\(l\)所过定点\(A\)的坐标;
\((\)Ⅱ\()\)求直线\(l\)被圆\(C\)所截得的弦长最短时\(m\)的值及最短弦长;
\((\)Ⅲ\()\)已知点\(M(-3,4)\),在直线\(MC\)上\((C\)为圆心\()\),存在定点\(N(\)异于点\(M)\),
满足:对于圆\(C\)上任一点\(P\),都有\( \dfrac {|PM|}{|PN|}\)为一常数,试求所有满足条件的点\(N\)的
坐标及该常数.