Move create_union_triangulation() and extract_boundary_mesh().

These functions were previously in GridTools, but conceptually they create
meshes and so should be in GridGenerator. Move them there but leave the
old functions in GridTools with a note that they are now deprecated.

Also structure the documentation of the functions in GridGenerator better.
Merge pull request #103 from bangerth/move-functions

These functions were previously in GridTools, but conceptually they create
meshes and so should be in GridGenerator. Move them there but leave the
old functions in GridTools with a note that they are now deprecated.

Also structure the documentation of the functions in GridGenerator better.
CMake: Remove non-functional code

This actually never worked...
CMake: Remove all "help" targets

It turns out that CMAKE_PROPERTY is too buggy to be useful. We cannot
set property CMP0037 to the old behavior in order to define a custom "help"
target in a macro without a warning. o_O
Merge pull request #104 from tamiko/cmake_fixes

Cmake fixes
Construct restriction and prolongation matrices on first request. This reduces construction time of high-order FE_Nedelec substantially.

Log changes.
Merge pull request #105 from bangerth/make-cast-explicit

Use an explicit cast when need a bool from optional<...>.
Merge pull request #106 from agrayver/optimize_fe_nedelec

Optimize construction of high-order FE_Nedelec by moving out some non-essential computations
Import BOOST 1.56.0.
Remove parts of the boost sublibraries that we don't need. Specifically, this applies to documentation and build directories.
Update test output.
Adapt a patch from around the internet to fix an issue with gcc 4.6.
Remove the fusion sublibrary as we apparently don't need it.
Also remove the spirit library.
Add a changelog entry.