ticket:10017: Added proposed C++ API for time periods along with sample code.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@33494 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10017: TimePeriod::forAmounts() to take a const TimeUnitAmount * const *

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@33497 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10017: Change signature of TimePeriod::getAmount()

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@33498 251d0590-4201-4cf1-90de-194747b24ca1