utils: fix deallocated memory in SpawnUnix

The function 'prepare_environment_variable' should allocate data with
new instead of malloc because the free_str_array use delete[].
devs: fix a potential segfault in Coordinator

A null pointer is used into the function to prepare a message in an exception.
vpz: remove useless assignment in CoupledModel

The value stored to the correct variable is never read between the while
and the assignment.
mvle: assign a default value to the number of VPZ
utils: simplify source in SpawnUnix

Since ::execve function does not return in success, we can simplify the
function.
template package: generalize the compilation

The package dependencies are now automatically checked during the configure
process using tags into cpp files (Closes #149)
- 'tagdepends' allows to declare package dependencies
- 'tagdynamics' is used to declare a vle dynamic
template: fix  FindGVLE.cmake

GVLE_LIBRARIES was relying on the VLE 1.1 version instead VLE 1.2
template: generalize Find*VLE.cmake files

Find*VLE scripts use now the VLE_ABI_VERSION variable in order to
search VLE libs and includes.
win32: fix the VleUtilsConfig.cmake file

- CMAKE_HOME_WIN32 is not a cmake usefull variable (use WIN32 instead)
- search for *.a libraries for packages dependencies
- fix vle libs path for package dependencies
template: fix VleUtilsConfig.cmake script

definition prefix in VleCheckPackage did not take into account the possibility
to have module version into package dependencies.
NEWS: update
cpack: fix installation of gtksourceview directory

The libgtksourceview-2.0 library needs the language template files for
cpp, cmake, txt files. The $VLE_GTK_PATH\\share\\gtksourceview-2.0
directory must be installed in the NSIS package.
gvle: switch from Gtkmm2 to Gtkmm3
Fixes for gtkmm3:

- remove unused mEditActionGroup in ConditionBox.hpp
- fix makeMenu of ConditionBox.cpp
- add dependency on cairomm (still needed)
- update gvle.pc file for compilation of extensions