[lang] Rename 'Scroll Mode' to 'Continuous' (#5169)

The current name causes people to think of scrolling, which is slightly awkward on E Ink. For example, see <https://github.com/koreader/koreader/issues/5166#issuecomment-517771475>.

> But this on LCD, not E-ink where the lag is unbearable, especially if you want to correct any scrolling over/undershoot.

Scroll mode is a misnomer. It should be renamed continuous. I use "scroll mode" as the default, but I seldom or never scroll. Conversely, you can still scroll in paged mode if a page is longer than the screen. As far as I'm concerned if you're scrolling (panning) you may be doing it wrong, but to anyone reading: you do you. ;-)

frontend/ui/data/koptoptions.lua

@@ -45,8 +45,8 @@ local KoptOptions = {
         options = {
             {
                 name = "page_scroll",
-                name_text = S.SCROLL_MODE,
-                toggle = {S.ON, S.OFF},
+                name_text = S.VIEW_MODE,
+                toggle = {S.VIEW_SCROLL, S.VIEW_PAGE},
                 values = {1, 0},
                 default_value = DSCROLL_MODE,
                 event = "SetScrollMode",

frontend/ui/data/strings.lua

@@ -6,7 +6,6 @@ S.SCREEN_MODE = _("Orientation")
 S.DUAL_PAGES = _("Dual Pages")
 S.PAGE_CROP = _("Page Crop")
 S.FULL_SCREEN = _("Full Screen")
-S.SCROLL_MODE = _("Scroll Mode")
 S.ZOOM_DPI = _("Zoom (dpi)")
 S.PAGE_MARGIN = _("Margin")
 S.H_PAGE_MARGINS = _("L/R Margins")
@@ -72,7 +71,7 @@ S.PORTRAIT = _("portrait")
 S.LANDSCAPE = _("landscape")
 S.REGULAR = _("regular")
 S.BOLD = _("bold")
-S.VIEW_SCROLL = _("scroll")
+S.VIEW_SCROLL = _("continuous")
 S.VIEW_PAGE = _("page")
 S.LTR = _("LTR")
 S.RTL = _("RTL")