share/examples: move examples into appropriate packages

Allow a new variable SE_xxxPACKAGE to be used to place an example group
into a package.

Move the following examples into existing appropriate packages:

• bhyve examples into FreeBSD-bhyve
• bootforth examples into FreeBSD-bootloader
• csh examples into FreeBSD-csh
• ipfw examples into FreeBSD-ipfw
• jail examples into FreeBSD-jail
• pf examples into FreeBSD-pf
• ppp examples into FreeBSD-ppp
• printing examples into FreeBSD-lp
• uefisign examples into FreeBSD-efi-tools
• ypldap examples into FreeBSD-yp
• hast examples into FreeBSD-hast

Move all other examples into the new 'FreeBSD-examples' package.

This removes a significant number of files from the FreeBSD-utilities
package.

Reviewed by: imp, manu
Pull Request: https://github.com/freebsd/freebsd-src/pull/1176