gnuplot-mode doesn't respect user's electric-indent-mode settings

[ShimmerFairy]

Normally, if you have electric-indent-mode disabled, then RET (aka C-m) does nothing more than insert a newline; if you want to insert a newline and automatically indent the next line, you'd type C-j to invoke newline-and-indent. However, gnuplot-mode clobbers the existing definition of RET to behave the same as C-j, which forces this behavior on users who have explicitly chosen not to use it:

    (define-key map "\C-m"        #'newline-and-indent)

The proper thing to do is to simply not do this at all; gnuplot-mode already sets the indent-line-function variable, and that's really all that's needed for electric-indent-mode to automatically indent whenever a newline is inserted. gnuplot-mode should be leaving all electricity-related functionality in the hands of that minor mode (this includes its remapping of the } key to gnuplot-electric-insert, which also shouldn't be done).