Migrate a couple of functions to gnc-plugins.c.

[David Hampton]

Log Message:
-----------
Migrate a couple of functions to gnc-plugins.c.

Tags:
----
gnucash-gnome2-dev

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/gnome:
        gnc-plugin.c
        gnc-plugin.h
    gnucash/src/gnome-utils:
        gnc-gnome-utils.c
        gnc-gnome-utils.h