CmakeLists.txt formatting and additional tests

Hi - I'm just getting started with this project. When I attempted to build headless, I ran into issues because I didn't have leveldb and miniupnpc installed (I'm running Debian Wheezy). I've added additional checks for the leveldb and miniupnpc headers and libraries. I tried to copy what was already in existence for libcrypto++. 

Please let me know if you would like this to be done differently. 

Thanks,
~C