added Broadie-Kaya exact simulation for the Heston model
added pricing engine for arbitrary European payoffs under the Heston
model
fixed formatting
updated VC10 files
Fixed file permissions
Updated VC++ and Dev-C++ projects.
Reordered files
Moved modified Bessel tests with tests for other functions
Merge pull request #73.

- added Broadie Kaya exact simulation schema;
- added pricing engine for arbitrary European payoffs under the
  Heston model;
- added modified Bessel functions.