mpkg: install: allow to install a specific version.
mpkg: install: allow to install a specific version.

Specify version by appending _<version>.

Example to install package a in version 1.0:
$ mpkg install a_1.0

Signed-off-by: Gaël PORTAY <1666f60cfa201a60b0ea694168a0b6932673170a@gmail.com>

gazoo74/mpkg,gazoo74/mpkg