Add script to setup FUSE mount after build.

[viveknigam3003]

Motivation

The build script handles the compilation of the program but does not set up FUSE in the way it can be used for mounting the Rucio server(s) to a directory using the FUSE mount. A post-build script is thus required to automate the process of setting up FUSE and mounting the server using the same.

Expected Result

vivek@ubuntu:~/Desktop/GSoC_2020/fuse-posix$ sudo ./postbuild.sh
Setting up FUSE for ruciofs.........
Done.

vivek@ubuntu:~/Desktop/GSoC_2020/fuse-posix$ ./cmake-build-debug/bin/rucio-fuse-main

Settings file at: ./settings.json
Parsing settings file:

	Server 0 -> rucio-dev-server:
		url = https://localhost/
		account = root

Actual Result

Manually set up FUSE. Add the user to the fuse group and set the right permissions.

[gabrielefronze]

Done for CentOS7 -> https://github.com/rucio/fuse-posix/blob/master/install-scripts/install-centos.sh