[#13] Added test script

At the moment we have 6 tests:
1) make -j4 should return 0
2) make clean should remove all .o, .a and .d files
3) the output of drampower for the trace in traces/commands.trace should match a reference output file, based on version 3.1.
4) the libdrampower test should build while linking to xerces.
5) the libdrampower test linked with xerces should produces output that matches a reference output file.
6) the libdrampower test should build while not linking to xerces.

Run them by calling 'make test'.