Remove instructions for building DUNE from source

A large portion of the instructions was for building DUNE from source
without providing any real benefit for someone starting with OPM
development.

Instead provide a link to a repository where backports of the necessary
packages can be downloaded. This will hopefully enable beginners to get
up to speed faster.
Improve diagnostic output if crossflow is detected.
Support shut wells in compressible tpfa solver.
Fix treatment of WELOPEN keyword.

Now you can actually shut and open wells with WELOPEN. The following
caveats apply:
 - this may interact improperly with group controls,
 - dynamic usage of WCONINJE/WCONPROD should not be mixed with WELOPEN.
Don't crash on models without wells.

The user will legitimately want to run models that do not specify wells
(e.g., using boundary conditions).  While we do not yet fully support
that configuration (no wells), we absolutely must not crash by
dereferencing null pointers or generating pointers into ::empty()
std::vector<>s.

This commit installs the required guards needed to avoid said failure
mode.
Merge pull request #29 from atgeirr/master

Handling shut wells, improved SWAT/SGAS init.
Add volumetic unit liter

For simulating laboratory experiments, liter is a more suitable base
unit than gallons or barrels.
Interpret ``wells != 0 && wells->W == 0'' as ``no wells''.

The CompressibleTpfa class always passes a non-null `forces->wells'
object to the constructor, assembly, and reconstruction routines but
uses ``forces->wells->W == 0'' to signify a simulation model without
wells.  This is, arguably, an error in the CompressibleTpfa class but
one that does not require a lot of work to support in the
cfs_tpfa_residual module.

Insert the extra tests in an effort to honour the ``liberal in what you
accept, strict in what you produce'' principle.
Merge remote-tracking branch 'upstream/master' into fix-impedance-mismatch
Merge pull request #30 from bska/fix-impedance-mismatch

Fix Impedance Mismatch Between CompressibleTpfa and cfs_tpfa_residual
Ignore executable for sim_2p_comp_reorder example

Actually, it is a libtool wrapper script, but it is automatically
generated anyway.
Ignore wrapper for lib.exe on Windows

This file is copied into the directory by newer versions of autoconf.
Avoid leading space in package name

By having an M4 line comment ("dnl") at the end of the line after the
comma, it seems that the indentation is included in the string on the
next line (it does not start at the escaping bracket).

This whitespace should be removed so the PACKAGE define can be used in
for instance filenames.
Provide pkgconfig files for library

A boilerplate .pc file is provided in the lib/pkgconfig directory. Using
this location has the advantage of being in the same path relative to
the libraries as it will be in the installation. The drawback is that the
lib/ directory no longer contains just output unless one uses out-of-tree
builds.

In the root directory of the project a local .pc file is provided which
instead of the usual end-installation directory rather points to the
build and source directories. By adding the build directory to the
PKG_CONFIG_PATH environment variable, a local build can be referred to
from other projects (such as examples or specific test-cases).

Having two different files is unfortunately necessary since pkgconfig
does not support prefix rewriting on Linux, and having them in two
different directories is necessary since the AutoMake-generated files
is not capable of renaming a file, only relocating it.
Merge pull request #31 from rolk/local-pkgconf

Support for pkg-config
Make LT_INIT recognizable by autoconf

The LT_INIT macro is wrapped in an m4_ifdef to handle older versions of
libtool. However, the text scanning done by libtoolize cause a warning
if this statement does not match a particular search expression.

Writing the clause in this form makes the (false) warning go away.
Disable warning for using DUNE's FieldVector::size

In DUNE 2.2 FieldVector::size changed from being a member to being a
method. A compatibility warning is issued if you include the relevant
headers.

This warning can be silenced for DUNE modules by using passing the
option --enable-fieldvector-size-is-method to ./configure. This patch
effectively does the same, but through a macro definition.
Merge pull request #33 from rolk/fieldvec

Disable warning for using DUNE's FieldVector::size
Merge pull request #32 from rolk/lt_init

Silence faulty warning from libtoolize about LT_INIT
Fix comment and indentation.