Merge pull request #200 from enviroCar/dev

Update from dev branch
Update lang_en.php
Merge pull request #202 from nuest/dev

fix HTML validity of about page, add new block for app
Update lang_en.php

removed sentence re: stable version due end of 2013.
added the mailto in $faq_a5
fixed contact
corrected link
changed links in get involved
Merge pull request #204 from enviroCar/dev

Dev
Added menu items for shapefile and csv download
Work with dev API for testing
Hide shapefile-download-button if there are too...

... many measurements to export the track.
Fix for #192
Added empty hrefs so pointer symbol is shown
Update lang_de.php
"The enviroCar app": linked app to google play
include crossOriginKeyword in OSM layer init
remove grayscale JS hack / use bw-mapnick instead
add simple php proxy for access to OSM tiles
add simple php proxy - now with proxy files