Force tmux to use 256 colours

So that themes in Vim work correctly under tmux, created an alias for
tmux to ensure that 256-color mode is set. Setting the colour mode in
the tmux.conf file did not seem to have any effect.

Change-Id: I50005153a6409e0ed99af7c722e7bd0cdd95a0df
Make tmux a little less green

Themed tmux a bit to tone down its default bright green colours.

Tidied up tmux.conf a bit too so that things do not conflict with the
new theme colours.

Change-Id: I859321fec0e0531d9b0f79eccb0be94c51fd86a8
BUG-ID:  N/A
Add multi-cursor plugin to vim

To help with editing multiple lines at once added a multi-cursor plugin
that allows editing similar to capabilities of Sublime Text editor.

Change-Id: I1ec5b4fc052a2e0fc821559d7425e67b23219083
BUG-ID:  N/A