output: restore the GVLE output plug-in

The GVLE output plug-in was removed in the previous patch. We re-enable
the code.
vle.output: fix missing gvle plugin storage

The gvle plugin storage was temporarly removed by error.
output: fix requirements for gtk+

Glade files required 2.24 version of gtk+ whereas only 2.23 version is
provided on win32.
decision : update for win32

- remove DllDefines since extension is now a static lib
- exports symbols are also removed
- add FindVLE and FindGVLE cmake scripts and rely on them for
finding vle and its gtkmm dependencies for win32
difference-equation: update for win32

- remove DllDefines since extension is now a static lib
- exports symbols are also removed
- add FIndVLE and FindGVLE scripts and rely on them for finding vle
and its gtkmm dependencies for win32
celldevs: update for win32

- remove DllDefines since extension is now a static lib
- exports symbols are also removed
- add FindVLE cmake script and rely on them for finding
vle on win32
cellqss : update for win32

- remove DllDefines since the extension is now a static lib
- exports symbols are also removed
- add FindVLE cmake script for findinf vle on win32
differential-equation: update for win32

- remove DllDefines since the extension is now a static lib
- exports symbols are also removed
- add a FindVLE script for finding vle on win32
- fix missing include (iostreams)
dsdevs: update for win32

- remove DllDefines since the extension is now a static lib
- export symbols are also removed
- add a FindVLE cmake script for finding vle on win32
fsa: update for win32

- remove DllDefines since the extension is now a static lib
- exports symbols are also removed
- add FindVLE and FindGVLE cmake scripts for finding vle on win32
- fix missing boost dependencies
petrinet: update for win32

- remove DllDefines since the extension is now a static lib
- exports symbols are also removed
- add a FindVLE and FindGVLE for finding vle on win32
forrester: update for win32

- add a FindGVLE cmake script for finding vle on win32
- fix missing boost dependencies
output: update for win32

add FindVLE and FindGVLE cmake scritps for finding vle on win32
examples: update fr win32

- add a FindVLE cmake script for finding VLE on win32
- add missing boost dependencies
- add missing iostream includes
forrester: update terminology

Little changes have been made to the terms used for the GUI.
(closes #17)