move all source files to src/
update .gitignore
update SDK
replace Botan with crypt_blowfish

Botan is just too much overkill
update licenses
massive code changes

these changes introduce syntax and behavior changes:
- it is now possible to specify custom callbacks + parameters
- no use of c++11 features, use of the boost libraries instead
- only one thread is used for hashing/checking
update .gitignore
added visual studio project files
added PAWN include file