Terminal: allow % in URLs.
Terminal preferences: replace "Cancel" with "Revert"

This is the standard way in Haiku preference panels.
Terminal Prefs: replace "OK" with "Defaults"

Again, this is the more standard way to do things in Haiku.
add window size and encoding to terminal prefs

* The menu items now only set the values for the current window without
saving,
* The settings in the preference window are persistent,
* The "save as defaults" menu item is removed.

Fixes #5030.