Massive overhaul of structure for Bash files

*   No longer using .bash_logout
*   No longer using .bash_profile, using POSIX-compliant .profile
*   instead; in particular, moved most of environment settings into
    .profile
*   Moved some of the separable functionality of both .profile and
    .bashrc into subdirectories (some scripts shared, some not)
*   Tidied implementation of ls/grep aliases
*   Updated install script to reflect all of the above
Let SSH_CONNECTION be updated in tmux env

But nothing else!