Cleanup of external dependencies install script

Initial work to cleanup and remove many unused dependencies from the install script, see #586 (closed).

As of now I identified the following essential packages for nrUE and gNB to work:

automake, build-essential, cmake, ninja-build, pkg-config, git, libatlas-base-dev, libblas-dev, libboost-dev, liblapack-dev, liblapacke-dev, libpython2.7-dev, libreadline-dev, libsctp-dev, libssl-dev, libtool, libxslt1-dev, libtasn1-6-dev, patch, openssl, xxd

Plus the specific package for each distribution, for example Ubuntu 20.04: libtasn1-6-dev, libgnutls28-dev, libconfig-dev, python, guile-2.0-dev

The following packages have been removed:

autoconf, cmake-curses-gui, curl, doxygen-gui, texlive-latex-base, ethtool, flex, g++, gcc, gdb, graphviz, gtkwave, iperf, iptables, libffi-dev, libffi-bin, libgmp-dev, libgtk-3-dev, libidn2-0-dev, libidn11-dev, libmysqlclient-dev, libusb-1.0-0-dev, libxml2, libxml2-dev, octave-signal, openssh-client, openssh-server, subversion, wget, libxpm-dev, libboost-all-dev

The following packages has been to the optional list of pkgs:

doxygen, libforms-bin, libforms-dev, xmlstarlet

wget is now installed only during bladerf install driver which is downloaded using it.

Additionally, in order to effectively remove the dependencies from xforms (and thus X) all the static references to the scope have been removed. It's still possible to build and use the scope as a shared library.