Changes releative permeability to synch with Mrst
The derivative of the relative permeability at the minimum saturation
are no longer zero
Changes in the 3p relperm definition
The relperm of water and gas is now evaluated at the water and gas
saturation, respectivly. The relperm of oil is still a combination of
the the 2p relperm of water/oil and oil/gas.
Equality is now treated as saturated
The calculated gas resolution factor is compared to
the tabulated resolution to check wether the oil is saturated
or not. The new test judges equality as saturated. This
is cruscial as the gas resolution is set to equal the tabulated value
for the saturated case in the appleyard process.
Compute initial saturations from surface volumes
Add new function is added that computes saturation from surface volumes
solving z = As for each cell. This function is used to compute an
intial guess to the saturations in initState_impl.hpp.
Change name to initBlackoilStateFromDeckUsingRS
The second input of initBlackoilStateFromDeck that computes surface
volumes based on gas/oil ratio is changed from
BlackoilPropertiesInterface to Props. To avoid duplication with the old
initBlackoilStateFromDeck its name is changed to
initBlackoilSurfvolUsingRS.
Added functions for b and mu with isSaturated as input.

Functions for volume factor and viscosity that explicitly take a boolean
variable indicating whether the fluid is saturated or not is added to
the SinglePvtInterface.

Corresponding changes are done in the dependent PVT files.

The new functionality is tested in test_blackoilfluid
Merge branch 'mrst' of github.com:totto82/opm-core into match-reference/properties
Sort headers into logical groups.

This is an aesthetic-only change.
Include <limits> for std::numeric_limits<> template
Add a facility for checking/assigning presence of free phases

This is intentionally black-oil specific because we presently do no
know how to handle other cases (e.g., more phases or number of phases
different from number of components).
Switch condition interface to phase presence facility

Commit a5a4d7b introduced density and viscosity evaluators into the
SinglePvtInterface that accepted an externally assignable condition
to distinguish saturated from unsaturated cases.  As a result of a
few low-level technical problems with that approach, this commit
changes those affected interfaces to use the black-oil specific
'PhasePresence' facility of commit a033329 instead.

Update tests and callers accordingly.

Suggested by: @andlaus
Approved by:  @atgeirr
Merge pull request #442 from bska/match-reference/properties

Synchronise Initialisation, Saturation Functions and PVT Models with MRST and ECLIPSE