Actually initialize densities_ member.
Add DUMP macro for debugging.
Corrected fluidDensity() function to account for dissolved gas.
Use DUMP macro in useful places.
Properly compute well pressure differentials.

Properly here means using a simple algorithm like
in CompressibleTpfa and ImpesTPFAAD.
Do not evaluate properties at well perforation pressures.

Always use quantities derived from cell properties.
Remove blank lines at EOF
Merge remote-tracking branch 'atgeirr/fully-implicit' into fully-implicit