OTAcctFunctor_PayDividend: factor out class to own file

This change revealed the circular dependency between OTServer and
OTAcctFunctor_PayDividend.
OTAcctFunctor_PayDividend: rename to AcctFunctor_PayDividend
cppcheck: define OT_FAIL as assert(false)

This macro definition helps cppcheck to correctly recognize
early exits.
Merge pull request #59 from toxeus/develop

OTAcctFunctor_PayDividend: factor out class to own file