Changes for using shared version of OpenRPT

This gives the user the option to use the following:

- shared library version of OpenRPT
- OpenRPT image files installed under /usr/share by the -dev package
- csvimp headers under /usr/include/csvimp or elsewhere (installed by a package)
- building libxtuplecommon as a shared object

To use:

```
export OPENRPT_HEADERS=/usr/include/openrpt
export OPENRPT_LIBDIR=/usr/lib/x86_64-linux-gnu
export OPENRPT_IMAGE_DIR=/usr/share/openrpt/OpenRPT/images
export USE_SHARED_OPENRPT=1

export CSVIMP_HEADERS=/usr/include/csvimp
export CSVIMP_LIBDIR=/usr/lib/x86_64-linux-gnu

export BUILD_XTCOMMON_SHARED=1

qmake

make
```