Add multidim mod simulation

Details:
- add a multidimensional simulation program
- correct the Modulator::bits_per_symbol() to take into account
  the dimension of the constellation
Update constellation

Details:
- add Constellation::getMinDistance() - returns the constellation's d_min value
Add high precision test

Details:
- add Point::operator==() high precision equality test
- make equality tests to ensure that ((a == b) && !(a !=b)) is true (instead of ordinary a == b)
Fix constellation building

Details:
- force building constellations with minimum dMin (internal feature -- no API is given).
  The problem at this point might to be very trivial but in fact a logical error occured
  because of building constellations with symbols very, very close to each other due to
  the numerical noise (sic!!!). Although the current implementation seems to be working
  as expected, the problem was rather worked-around than solved. The other fallacy is that
  the current implementation is extremely slow, so it can take a while to generate the
  constellation (ConstellationBuilder::build() is very slow, rest is as it was).
  the current implementation seems to be working as expected. Al