Reorganize Porter's Handbook a little

• Create new section "pkg-plist" after 13.4 pkg-req
• Move 13.5 Changing pkg-plist based on make variables under newly created pkg-plist section
• Move 17.11 Cleaning up empty directories under new pkg-plist section
• Move 17.16 Configuration files under new pkg-plist section
• Move 19 Automated package list creation under new pkg-plist section

• Move 7 MASTERDIR chapter into 5 Configure the Makefile chapter
• Move 9 Manpages and 12 Info files chapters into 5 Configure the Makefile chapter

This commit basically moves a large untouched blocks of text around,
editing will be done later as separate commit, to ease the job for translators.

Approved by: keramida (mentor)
Review by: linimon, silence on doc, silence on portmgr