Fixed hard-to-find lua files and added Makefile targets

sosi2osm now looks for .lua files in /usr/local/share/sosi2osm/lua
and /usr/share/sosi2osm/lua if it cannot find the file in
./lua. This means that it is now possible to run sosi2osm from
wherever.

New Makefile target: install  - installs binary and lua files to
/usr/local/..

New Makefile target: uninstall  - removes all the files and folders
installed by install.

It looks for header files for libfyba also in /usr/include/..  now.