Use pkgng glob (-g) feature to allow installation of packages by wildcard

Also solves the particular problem of installing packages that have multiple versions in the repo, but specifying the exact version would be troublesome:

$ pkg install -n dovecot
The following 2 packages will be installed:

	Installing dovecot: 1.2.17
	Reinstalling dovecot-2.2.6 (options changed)

$ pkg install -n dovecot-2.2.6
The following 1 packages will be installed:

	Reinstalling dovecot-2.2.6 (options changed)

$ pkg install -n -g dovecot-2*
The following 1 packages will be installed:

	Reinstalling dovecot-2.2.6 (options changed)