Is there a All-In-One Bike that I can use for several types of riding?
In general you can get an very good all-around road bike, or a very good all-around mountain bike.  To get a single bike for everything there will always be trade-offs in areas like weight/durability; speed/traction; etc.

That said - many people own one bike and use it for everything.  If I had to drop to one bike I would buy a 29"-wheel based front suspension mountain bike with the following:


suspension front fork with lockout
disk brakes 
rack and fender mounts (and a rack and fenders)
a spare wheelset


In my mind the spare wheelset is key - that way you can run a high pressure slick on one set, and then switch to a knobbie without the hassle of swapping out the tires on each wheel.