vle: remove useless dependencies

The Boost::Asio does not depend to openssl libssh2 libssl libidn gnutls
hogweed libcrypto nettle. So we remove them.
vle: restore the libxml2 initialization

We restore the xmlInitParser() in vle::Init constructor.
utils: add unit test for DownloadManager

We add a test in DownloadManager. This unit test check the download of
the vle-1.0.0.dtd from www.vle-project.org server. We use BOOST_CHECK
instead of BOOST_REQUIRE.
utils: export DownloadManager symbols

To use DownloadManager class from external prorgam (as unit test), we
need to export the symbols.
utils: fix coding style in DownloadManager

Fix several coding style errors.
utils: add -DWITH_DOC -DWITH_TEST in Preferences

We add the two options WITH_DOC and WITH_TEST in Preferences. Theses
options are used when the users selects the configure package mode.
vle: fix executable status return

The status of the executable is badly in the package mode, if now no vpz
provided. For example, the following commands failed (even if rclean
success):

	$ vle-1.1 -P vle.output rclean
manager: fix logOptions structure

Remove the last comma of the structure.
An error occurs  during compilation.
template: fix the cmake script

Replace into VleCheckAndDeclareGeneratedModelsConfig.cmake
the lokk for differentialEquation by differential-equation
Merge pull request #57 from rtrepos/master

Taking into account differential-equation extension and fix a struct in manager.
utils: make Spawn.hpp public

GVLE needs to use the Spawn module. We move the Spawn.hpp file from
details into public API.
utils: enhance Spawn::isfinish

We need to ensure that the is_running function is call one time at
least. So, we fix the Spawn::isfinish function.
gvle: add a SpawnPool member to the GVLE class

- In order to manage many spawns used at the same time, a spawn
  container is added to the GVLE main GUI class. This container
  automatically erase spawns when they are not any more used.
- The OpenFile feature of the file Tree View widget has been updated in
  order to use the spawn system of VLE.
vle: allow assign local to POSIX

By default, VLE use the locale according to the environment variables.
In library mode, a "POSIX" or "C" locale can be used. We add a new
constructor to to vle::Init class to permit "POSIX" locale.
vle: add WITH_COVERAGE option in CMake

We need to perform coverage test in VLE. So, we add the gcc `--coverage'
option in CFLAGS, CXXFLAGS and LDFLAGS if the user selects the
WITH_COVERAGE option in CMake.
value: remove boost::serialization depends

Since VLE 1.1 does not (de)serialize value between components, we can
remove this dependency to Boost.
template: assign default path for scripts

Assign a default path scripts Vle*.cmake since CMake complains to not
found these scripts.
utils: split source/binary package

We change the behaviour of packages in VLE. Now, the VLE_HOME directory
stores only the binary version of packages. The source code must be
anywhere on the system.

For example, the source package is in $HOME:
$ cd $HOME
$ vle -P foo create

The binary package goes to the $VLE_HOME/pkgs-1.1 directory:
$ vle -P foo configure build
$ ls $VLE_HOME/pkgs-1.1/foo
Authors.txt  Description.txt  exp          News.txt  plugins
data         doc              License.txt  output    Readme.txt
vle: allow building of VLE with old system

We allow to build VLE (but without Gvle) on old system i.e. with
libarchive 2.8.x and boost and boost asio <= 1.41
vpz: add missing iterator header

Add the iterator standard header. This file is missing in Views for some
compiler/architecture.