Add the install_package option

This option can be used in a script when you need to install a
package. The packages to be installed should be set in option
pkg_name. It will use apt-get on Debian/Ubuntu, yum on Fedora,
zypper on openSUSE and urpmi on Mageia/Mandriva.
Rename project to rbm (Reproducible Build Manager)
Set default timestamp to 2000-01-01 for projects without a git_url
Make it possible to share input files definitions

Instead of a file descriptor hash, an element of the input_files array
can be a string. In that case the string is the name of the option
containing the file descriptor hash. This can be useful when you are
using the same file in multiple projects.
install_package: fix dpkg command to check for installed package