ignore warnings originating from eigen
cmake: fix algo headers install
fix tests/common.hh

There were two bugs. When the result file happened to be

    WAIST
    nan
    nan
    nan
    nan
    nan
    nan

    WAIST_P
    40.9789

it failed to convert nan to double (as expected) but then kept
trying until succeding with 40.9789 instead of just reporting its
failure.

With this bug fixed, it reported the failure, but against the wrong index
(always 0).
spatial: uniformize constructors and initializers

Several changes:

 * add Zero() initializers to Force, Inertia and ltI.

 * change the behaviour of ltI constructor, which was initializing the values to
   zero. Now it lets them uninitialized.

 * clean up ltI a bit: make it a class instead of a struct, remove tabs, simplify
   computations.

Note that Motion already had a Zero method and Transform had Identity.

This fixes issue #41.
spatial: fix style
robotbuilder: replace auto_ptr with good old ptr

because the auto_ptr causes warning C4251: need to have DLL interface
on visual studio.