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.
gvle: add the GlobalPlugin system

In order to customize deeply the gvle GUI, a GlobalPlugin class has
been added. It does allow to add widget to the GUI.
- Gvle has been enhanced to check fo each global plugin availabe and
  to run them.
- The PluginFactory has been changed in order to keep during all the
  session the already loaded plugin available, insteed of relaxing the
  ressources as soon as a plugin has been used once.
gvle: fix the bug of the Project menu

Due to a change of the spawn managment system, the Project menu was
available only once.  After the usage of a menu entry like Configure,
the menu was not available anymore. The way to use the package methods
has been changed in order to fix this bug.
cmake: remove chrono library if find_boost fails

We need to check if the chrono library is available. If it not, we need
to run find_boost twice without chrono.
all: update to gcc 4.4.6

We change source code in many files to use GCC 4.4.6.
vle: update README

Update the README file with newest dependency.
gvle: fix the plugin file generation

gvle assume that the folder loaded is a project working directory. It
does keep it as a member field. And when a plugin does want to save a
generated file, the expected place is the "src" subdirectory of the
project source directory (Closes #63,#62).
gvle: add before to simulate always build

The opportunity to always configure, build and install the package has
been made available. This feature can be disable with the new
configuration switch gvle.packages.auto-build.
vle, gvle: fix includes

some includes were missing.
utils: update the package API

- Remove the package singleton and provide a public constructor.
- Make the distinction of the source and binary package in the API using
  the enum type (PKG_BINARY, PKG_SOURCE).
- Add a package instance to GVLE.
- Add the argument curr_package to gvle modelling plugins.
- Output files are now generated into the current dir for vle and rvle
  and into <current_package>/output into gvle.