Add helpers grad, fullngrad, fulldiv.
Let sim_2p_comp_ad throw if not given an input deck.

There is some code in place now to create wells for the no-deck case,
but since it does not work correctly yet, the simulator intercepts this
and throws.
Remove unnecessary include statement.
Rename AutoDiff::Forward -> Opm::AutoDiff.
Rename AutoDiff::ForwardBlock -> Opm::AutoDiffBlock.

Also moved AutoDiffHelpers.hpp content to Opm namespace, and modified other
files as required by these two changes.
Documented AutoDiffBlock.
Documentation refinement. Added main doc file.
Renamed misleading adfi -> fi.

Some classes and a program were renamed since they were not fully implicit
solvers despite their names indicating it.
Compute gravity potensial using the face average as in Eclipse and Mrst
Added an option to write well reports to a .mat file
Document class BlackoilPropsAd.
Require deck and remove simple source term in fully implicit sim.
Documented BlackoilPropsAdFromDeck.
Documented class DerivedGeology.
Documented class FullyImplicitBlackoilSolver.
Fix minor issues pointed out by bska.
1. The geo_.z() is now called directly instead of first converted to ADB
vector
2. Added some whitespaces fro readability
Expanded README.md, now similar to README in opm-core.
Updated to address points raised by bska.
Revert " Use MultiArch-unaware path for dune.module"

This reverts commit 512d49c41a73189871d0c69c5a9616f89236db03.