Install header-only pkgconfig file to generic lib/

The previous version assumed that we had libraries, and thus always
installs the .pc file in the multi-arch library directory. However,
we now have modules which does not have a library, but whose header
files still need to be located. Since the lib/ directory is usually
in the pkgconfig search path, it is natural to put them there.
Merge pull request #48 from bska/048_cmake

Synchronise build system with opm-core
Fix convergence failure exception message

The message was a leftover from the ImpesTPFA solver and should
reflect the actual location.

Noticed by: qilicun (Liu Ming)
Fixes: Issue #50
Merge pull request #51 from bska/fix-exception-message

Fix convergence failure exception message
add debian packaging
loosen tolerance a bit to avoid failing tests on certain archs (i386, precise)
Merge pull request #53 from akva2/loosen_tolerance

loosen tolerance a bit to avoid failing tests on certain archs
Add new AutoDiffBlock::constant() overload without block sizes.

This should simplify some uses of the autodiff code. The internals
have been changed to allow for objects to have an empty vector of
Jacobians, always treating that object as a constant.
Fix minor whitespace issue.
Fix bug in operator+ introduced by previous commit.

Also make documentation clearer.
Avoid infinite loop with two constant operands.
Reduce version to 0.9.

Since there is a fair chance of interface adjustments after the release,
the version number cautions the user a little bit more than calling it 1.0.
Merge pull request #54 from atgeirr/allow-empty-jac

Add new AutoDiffBlock::constant() overload without block sizes.