Solution.java:
- Added a method for checking if the solution as at least 1 replica in
at least one hour of the day.
- Now the method getCost() returns a float instead of a double, so the
value is more compact.

SolutionMulti.java:
- Added a method for removing a solution.
- Added a method for removing all the useless solutions (that are those
with always 0 replicas).
- Now the method getCost() returns a float instead of a double, so the
value is more compact.

Other fixes for the private cloud thing.