Add required packages for compiling

Required packages are: zip, kpartx
Expanded the list of required packages and changed the formatting of that list.
Added info on the Model B+.
Updated the project URL.
Fixed some formatting issues.
Rephrased a line to make it more clear.
Added a line break before the Model B+ part.
Fixed spelling error (2x to after each other).
Specified that you only need to provide options which you wish to override.
Fixed formatting issue (again).
Moved setting of the time right after the network has come online.

Also removed the old commented out code, since that's what a VCS is for.
Add logging functionality.

Everything that gets logged on the screen is now also logged to file.
With successful installations, the log file will be at
/var/log/raspbian-ua-netinst.log.
When installation fails, the log file will be put on the sdcard (normally
mounted on /boot) and will be named raspian-ua-netinst-<datetimestamp>.log.
Changed header style from Setext to atx.

This allows for more heading levels.
Added info on Model B+ support and added a section about logging.
Fixed check for the existence of previous error log files.

The '-f' parameter of test ie '[' expects a single file and seems to
error out on wildcards.
Solution found at
http://stackoverflow.com/questions/6363441/check-if-a-file-exists-with-wildcard-in-shell-script
Added code which installs libraspberrypi-bin from the raspbian archive.

This adds the 'vcgencmd' and friends to the system.
Done this by creating a apt preferences file and installing the package.
Fixes issue #65.
Include customs installation files in zip

If installer-config.txt and post-install.txt are present in the directory, these files are copied in the zip file.
When the zip file is uncompressed on sd, the customs installation files are already available.
Modified PATH to match that of root on a standard Debian/raspbian system.
Added support for serial console on installed system.

This fixes issue #57.
Added support to view kernel messages on the serial console.

So far it looks like userland messages can't be shown on both the screen
(tty1) and the serial console.
If it turns out to be possible, we'll add that later.