cmake: update FindVLE and FindGVLE

- related to commit 550d21096be9c8a0d965b3617a11a707c697be03 of vle
- related to commit 2bc632b82032f9caa78cd66a30dc740e81de3f30 of vle
- related to commit d1a8cfd63cc6610a1d447300f2ef2f949f921909 of vle
- related to commit 39f3bdca3e7cf944494b6f8dc939c69f7f9c6903 of vle
forrester: update the observables generator

Observables are not removed each time a model is regenerated.  If the
observable exist it is keeped, and if a observable is not any more
needed it is removed.
(closes #36)
forrester: update the Conditions

The variables initialisation system has been updated. Atomic double
port parameter are used in order to ease analyses with R. Each
Variables will have a port parameter with its name and its initiial
value.
(closes #44)
forrester: fix the drawing area refreshment

The pixmap needed to be resized at the wright time, followed by a
queueRedraw.
(closes #46)
differential: set a default initialisation

An initialization is required for all states variables.
Otherwise an exception is thrown. We modify this behavior
by setting a default initilialization value to 0 for variables
that are not explicitely initialized. (Closes #42)
differential: allow the update of state variables

- add an operator= for Var which updates the state value
- add a constructor that initializes the value
- add a const access operator to the state value (for observation)
differential: simplify the initialisation

Variables can now be initialised using the InitEventList as the container of
initialisedvalues. The vpz Ladybirdplantlouse is modified for testing
purpose (Closes #41).
all: fix CPack directives

The binaries are now built into "buildvle" directory. This directory is
now ignored when packaging.
muParser: fix the name of the CMake project

The name of the project now matches the name of the pkg.
decision: fix the data directory management

A new port parameter is generated by the modeling plugin. the
PackageName parameter tell where to load the plan file.
(closes #51)
package-1.1.0-beta2
ChangeLog: removed

We remove ChangeLog from repository.
README: switch to rst
README: add ext.muparser and vle.forrester

The repository have now ext.muparser and vle.forrester packages.
README: update
decision: fix the plugin selection management

The member data structure of the drawing area dedicated to the
selection where not reset when the modeling plugin were reuse inisde a
gvle session.
(closes #55)
decision: fix the plugin model settings

When finished to edit a model with the modeling plugin, the generated
dynamic, and the generated experimental conditions are set to the
model.
(closes #56)
all: fix Description files

- add missing Build-Depends, Conflicts, Url, Size, MD5sum fields
- add missing 's' to Tag field
- add a space before the dot of the end of description
output: add a flushbybag output option

This option enable to take advantage of event views. If set the output
plugin does flush datas by bags. This enable to have many outputs at the
same date. By the way the gvle plugin that enable the configuration has
been updated inside the GUI. (closes #59)
README: update