Fix build 2 errors on Fedora

add boost-devel to linux autobuild script and include string.h to png target.
Make toolbox translatable again.
Add appdata file

Applications wishing to have long descriptions, screenshots and other useful things
are required to ship one or more files in /usr/share/appdata/%{id}.appdata.xml.
see pttp://people.freedesktop.org/~hughsient/appdata/
Merge pull request #86 from jcome/jcome

Fix build 2 errors on Fedora