Adding DOC file about terminal colors.

This is the first doc file, so is the introduction of the doc folder
that should contain generic info and discusions. In the case of this
first file, ir contain info about the bultin color schemes in
gnome-terminal so it can be replicated in other terminal emulators. Also
some fancy color I found to use with the terminal.
Changing color palette of URXVT to tango theme.

The tango theme is a builtin theme for the gnome terminal and has some
blue tones that work good with foregrounds annd backgrounds of varying
tones and it don't burn your eyes.
Adding smear.sh script.

smear.sh clear the screen in a nice way to use between two calls to
commands with too much output, like a make or gcc execution, so there is
a noticeable space before the start of the output of a command.