Add script for automatic install on Ubuntu

This commit adds a script that allows users to install the core
library and all its dependencies with a single command on Ubuntu
machines.
Minor documentation and configuration updates

This commit adds minor updates to the documentation and configuration
files of the core library
Remove dependency from mako when not using ns2

This commit moves the import of mako package (used to export
topologies to ns-2) from the ns2 module to inside the to_ns2
function.

As a result, if ns-2 export is not used, it is possible to use
the FNSS core library without the mako package.