bashrc: enhance PATH, make firefox quicker, and auto logout

Make PATH to be constructuted somewhat reasonable way at login, which
should speed up finding a command from path later on.  The firefox
quickess comes from disabling font rendering support for some exotic
languages (PANGO stuff), and the 30 minutes TMOUT for bash is
reintroduced.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>