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.
win32: rely on native compilation

- boost dll are used rather than static libs
- static vle libraries are removed
- cpack is modified for native compilation
- note: test_package is temporarely removed because
it requires some fixes
TEMP: ajout buildAll.txt
win32: fix m_prefix path setting

m_prefix was initialized using HKEY_CURRENT_USER even if it is not set
TMP: win32: fix test_package