help: Updated appearance page, removed theme list

Removed list of available themes to reduce maintenance and translation
burden as per kittykat's suggestion.

https://bugzilla.gnome.org/show_bug.cgi?id=726736
Added hu to HELP_LINGUAS
Hungarian translation added by Balázs Úr <urbalazs at gmail dot com>
Updated Basque language
Updated Czech translation
Updated French translation
Updated French translation
Updated Spanish translation
prepare 3.12.0
Fix "fullscren" typo in gschema
help: basics.page: Added new game from toolbar

An instruction for starting a new game from the toolbar with accompanying
image has been included.

https://bugzilla.gnome.org/show_bug.cgi?id=726736
help: controls-default: Key, reformat & alttext

The key for staying in place has been edited to "Begin" (i.e. without
numlock activated) to match all other key descriptions e.g. "PgUp", with
a note that some keyboards only show "5" on this key. Table reformatted.
Alt text added for images.

https://bugzilla.gnome.org/show_bug.cgi?id=726736
help: New images w/ makefile, updated scores.page

New images of robots have been included for the themes not already
documented (anthills, cows, eggs. mice, spills, stormclouds,
toasters). "gnome-high-risk.png" and "gnome-low-risk.png" have been
renamed to "gnomes-high-risk.png" and "gnomes-low-risk" to conform
with theme name "gnomes" and names for the images of other themes.
One image for starting a new game added. Makefile.am was updated to
include new images.

The section on high and low risk robots now covers robots of all themes,
with the images added used to illustrate high- and low-risk robots.
Anthills, cows, eggs, mice, spills, stormclouds were all previously
missing. The information is now in table form, to improve concision and
reduce repetition. Information on viewing high scores has been added.
Alt text has been added to all images.

https://bugzilla.gnome.org/show_bug.cgi?id=726736
help: Reordered & formatted table of game types

The game types are now listed in the order in which they appear in the
preferences dialog; the previous order appeared to have no particular
pattern. The table has been reformatted to correspond better with the
formatting of other tables in GNOME Games. Section links are updated.

https://bugzilla.gnome.org/show_bug.cgi?id=726736
help: controls-default: Key, reformat & alttext

The key for staying in place has been edited to "Begin" (i.e. without
numlock activated) to match all other key descriptions e.g. "PgUp", with
a note that some keyboards only show "5" on this key. Table reformatted.
Alt text added for images.

https://bugzilla.gnome.org/show_bug.cgi?id=726736