pkg add: Allow event output to be recursive to fix output.

Use a tree output to make it more clear what is happening.
install/upgrade are not affected by this as they still have a job and
use proper ordering. pkg add needs special handling since it will start
installing deps in the middle of installing a package, and its deps may
start installing deps as well.

This is somewhat of a hack. It would be better to create a real job out
of the pkg add needs before processing anything.

  # pkg add /var/cache/pkg/libreoffice-4.2.5_4-8f497a08ab.txz
  Installing libreoffice-4.2.5_4...
  `-- Installing GentiumBasic-110_1...
  `-- Extracting GentiumBasic-110_1: 100%
  `-- Installing clucene-2.3.3.4_4...
  `-- Extracting clucene-2.3.3.4_4: 100%
  `-- Installing crosextrafonts-caladea-20130214...
  `-- Extracting crosextrafonts-caladea-20130214: 100%
  `-- Installing crosextrafonts-carlito-20130920...
  `-- Extracting crosextrafonts-carlito-20130920: 100%
  `-- Installing desktop-file-utils-0.22_1...
  `-- Extracting desktop-file-utils-0.22_1: 100%
  `-- Installing hunspell-1.3.3...
  `-- Extracting hunspell-1.3.3: 100%
  `-- Installing hyphen-2.8.7_1...
  `-- Extracting hyphen-2.8.7_1: 100%
  `-- Installing libabw00-0.0.2...
  |   `-- Installing libwpd-0.9.9_1...
  |   | `-- Installing libgsf-1.14.28_1...
  |   | `-- Extracting libgsf-1.14.28_1: 100%
  |   `-- Extracting libwpd-0.9.9_1: 100%
  `-- Extracting libabw00-0.0.2: 100%
  `-- Installing libcdr-0.0.16_1...
  |   `-- Installing libwpg-0.2.2_2...
  |   `-- Extracting libwpg-0.2.2_2: 100%
  `-- Extracting libcdr-0.0.16_1: 100%
  `-- Installing libcmis-0.4.1_3...
  `-- Extracting libcmis-0.4.1_3: 100%
  `-- Installing libe-book00-0.0.3...
  `-- Extracting libe-book00-0.0.3: 100%
  `-- Installing liberation-fonts-ttf-2.00.1,1...
  `-- Extracting liberation-fonts-ttf-2.00.1,1: 100%
  `-- Installing libexttextcat-3.4.4...
  `-- Extracting libexttextcat-3.4.4: 100%
  `-- Installing libfreehand00-0.0.0...
  `-- Extracting libfreehand00-0.0.0: 100%
  `-- Installing liblangtag-0.5.4...
  `-- Extracting liblangtag-0.5.4: 100%
  `-- Installing libmspub-0.0.6_2...
  `-- Extracting libmspub-0.0.6_2: 100%
  `-- Installing libmwaw-0.2.0...
  `-- Extracting libmwaw-0.2.0: 100%
  `-- Installing libodfgen-0.0.4_2...
  |   `-- Installing libetonyek-0.0.4...
  |   `-- Extracting libetonyek-0.0.4: 100%
  `-- Extracting libodfgen-0.0.4_2: 100%
  `-- Installing liborcus-0.5.2...
  |   `-- Installing libzip-0.11.2_1...
  |   `-- Extracting libzip-0.11.2_1: 100%
  `-- Extracting liborcus-0.5.2: 100%
  `-- Installing libvisio-0.0.31_2...
  `-- Extracting libvisio-0.0.31_2: 100%
  `-- Installing libwps-0.2.9_2...
  `-- Extracting libwps-0.2.9_2: 100%
  `-- Installing linuxlibertine-g-20120116...
  `-- Extracting linuxlibertine-g-20120116: 100%
  /usr/local/lib/X11/fonts/LinLibertineG: caching, new cache contents: 10 fonts, 0 dirs
  /usr/local/lib/X11/fonts/LinLibertineG: caching, new cache contents: 10 fonts, 0 dirs
  /var/db/fontconfig: cleaning cache directory
  /root/.cache/fontconfig: not cleaning non-existent cache directory
  /root/.fontconfig: not cleaning non-existent cache directory
  /usr/local/bin/fc-cache: succeeded
  `-- Installing lp_solve-5.5.2.0...
  `-- Extracting lp_solve-5.5.2.0: 100%
  `-- Installing mythes-1.2.4...
  `-- Extracting mythes-1.2.4: 100%
  `-- Installing nss-3.16.3...
  |   `-- Installing nspr-4.10.6...
  |   `-- Extracting nspr-4.10.6: 100%
  `-- Extracting nss-3.16.3: 100%
  `-- Installing poppler-0.24.5_4...
  |   `-- Installing openjpeg15-1.5.2...
  |   `-- Extracting openjpeg15-1.5.2: 100%
  |   `-- Installing poppler-data-0.4.6...
  |   `-- Extracting poppler-data-0.4.6: 100%
  `-- Extracting poppler-0.24.5_4: 100%
  `-- Installing redland-1.0.17_3...
  |   `-- Installing libltdl-2.4.2_3...
  |   | `-- Installing indexinfo-0.2...
  |   | `-- Extracting indexinfo-0.2: 100%
  |   `-- Extracting libltdl-2.4.2_3: 100%
  |   `-- Installing raptor2-2.0.14...
  |   | `-- Installing yajl-2.1.0...
  |   | `-- Extracting yajl-2.1.0: 100%
  |   `-- Extracting raptor2-2.0.14: 100%
  |   `-- Installing rasqal-0.9.32_1...
  |   `-- Extracting rasqal-0.9.32_1: 100%
  `-- Extracting redland-1.0.17_3: 100%
  Extracting libreoffice-4.2.5_4: 100%

Issue:	#923
Also split out deleting files

Removes need for special handling of 0-sized archives in do_extract() and
pkg_delete_files().

  # pkg delete -f git apache24 xorg
  [1/3] Deinstalling git-2.0.2_1...
  Updating /etc/shells
  ==> You should manually remove the "git_daemon" user.
  [1/3] Deleting files for git-2.0.2_1: 100%
  [2/3] Deinstalling apache24-2.4.10_1...
  /usr/local/etc/apache24/httpd.conf
  [2/3] Deleting files for apache24-2.4.10_1: 100%
  [3/3] Deinstalling xorg-7.7...

Issue:	#758