Add test cases for randmodel topologies with user-provided seed

This commit adds test cases to validate that all random topology
generators behave correctly when seeds are provided. These test cases
have been added to prevent the reappearance of the issue corrected
by #11.
Change Java package name from uk.ac.ucl.ee.fnss to io.github.fnss

This commit changes the name of the main package of the Java library
from *uk.ac.ucl.ee.fnss* to *io.github.fnss* since the latter domain
is simpler to remember and is the domain on which the FNSS website is
currently hosted.
Update README files and documentation throughout the codebase

This commit revises the content of README files and documentation to
reflect the current status of the toolchain.