Tidy module initialisation functions

Tidy module initialisation functions
* eshell/em-term.el (eshell-visual-command-p): New function.
(eshell-term-initialize): Move long lambda to separate function eshell-visual-command-p.
* eshell/em-dirs.el (eshell-dirs-initialise): Add missing #' to lambda.
* eshell/em-script.el (eshell-script-initialize): Add missing #' to lambda.