BUILD: Fix missing files in glob

JUCE files are suffixed with .cpp, hence this scheme has been added.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
IMPLEMENTATION/PLUGIN/VST: Increase default program number to 1

Some audio hosts do not handle well a null program number.
For this reason JUCE has a built-in assert about this, that we prevent
from firing with this change.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>