decision: refactoring tooltips
Revert "decision: refactoring tooltips"

This reverts commit 498d8ca7bda2e40eda55a520fd83b4143c3d1506.
Merge branch 'decision' of git://github.com/Chabrier/packages
all pkgs: update according the new Package API

- take into account the curr_package parameter for Modelling plugins
- update tests using a package instance rather than the singleton
forrester: modify the variable dialog

Variables item can be edited at the same level of expressivity than a
flow item. Variables can be linked with parameters item, compartment
item and exogeneous variables.
- The variable dialog has been removed.
- The flow dialog has been modified in order to be used for variable
and flow items.
- The variable item has been enhanced to carry more information.
(closes #19, #20)
muparser: fix missing doc/CMakeLists.txt

The file doc/CMakeLists.txt is missing and the CMake process fails. So,
we add an empty doc/CMakeLists.txt.