.gitignore: Ignored build directory.
Many improvements to make script.

Now only compiles files needed to be compiled (object file older than
header or source file itself). This make compilation much faster!

Stores objects files in directory specified via `meta.dat` file. Added
this field to meta file.

Also, slight improvements to printouts and such.
gaussiandeviate.*: Slight rewritings and creation of header file because of problems with duplicate symbols.
main.cpp: Added main file.
System.*: Small fixes. Added initialization of normal instances.
Particle.cpp: Corrected typos.