Create empty mining-activity

Created with "./createit.sh mining".
Change copyright information

I hope, this is ok that way.
Fill empty template with mining-activity code

Ok, the first playable version of the mining-activity is ready. This
took me a few days, but now it's time to commit it! :)

Bugfixes and enhancements will follow. ;)

I adopted some ideas and "ways to do" from other activities like:
  - hexagon
  - penalty
  - seerace
  - anim

Thanks for your work!
Add mining-activity's resources dir to make system

In order to have "make install" install the "rockwall.svgz" file, the
following make files had to be changed.
Until now, I only tested the mining-activity with:
  cd src
  ./runit.sh mining-activity

Again, the penalty-activity was the archetype, I copied from.
Fix mining-activity: bonus sound played twice

"gcompris.bonus.display()" already plays the bonus sound, so we don't
have to. This only leads to this sound being played twice.
Fix: mining-activity: no scrolling while bonus

We remember the pause state, so we can block input (scrolling /
mouseclicks), while in pause.
This forced to make the is_game_paused() function to be availably in the
Viewport class, so the Viewport's contructor had to be changed, too:
In order to pass every callback function, we pass the activity object
itself and the Viewport takes, what it needs.
Fix: mining-activity: code style

I made the eclipse code formatter to tidy up the source code a little
bit.
Fix: mining-acitivity: no nugget behind gc-bar

There are certain places on the screen, where no gold nugget should be
placed. This commit introduces a mechanism to define those areas and to
test possible nugget places against those constraints.

So far: A nugget will not be placed behind the GCompris bar in the
lower, left corner and not in front of the wood pillars on the screen
edges.
minor: fixed some typos
minor: add TODO to draw lorry with counter
minor: use correct LION bonus name after bug fixed
Add random stone decorations for each level

The Decorations class adds some random stone decorations to the viewport,
while the Placer class prevents objects (stones / goldnugget) from
overlapping with each other, the outer border or the gcompris bar.
Add safety counter to prevent endless while-loop

Keeping the number of decorations at 10, the case of not finding a valid
position seems to be veeeery unlikely. But if someone modifies game
parameters like the number of decorations or max decoration scale, we
don't want the application to freeze, because of running in an endless
while loop.
minor: code formatter removed space at end of line
Add nugget-counter-lorry to mining-activity

In order to see the number of currently collected nuggets and the total
number of nuggets to collect in this level, a lorry was added in the
lower right corner of the screen, showing this information.
Add lorry-icon for mining-activity

We can use the lorry, just added to the mining-activitiy as
nugget-counter-display, also as menu icon. ;)
minor: cleanup mining-act. by inkscape vacuum defs

Removed some unused definitions in the svg files, using inkscape
function "Vacuum Defs". No need to ship unused data around the world.
Complete board xml file for mining activity
Add sounds to mining activity

Both sounds have been provided by tuxpaint under GPL. Thanks for this
work and sharing it for free!

 - realrainbow.ogg has been copied as is
 - metalpaint.wav has been remixed by me to pickaxe.ogg
minor fix to keep text layout in translation

Adding 'xml:space="preserve"' makes intltool-update respect
newline-characters. So we can keep the layout of the texts also in
translations. Otherwise all newline-characters would be removed.
(Copied form "boards/menu.xml.in")

But this means to use newlines realy only, where new lines should begin.