Added some getters.

git-svn-id: http://svn.finmath.net/finmath%20lib/trunk@1338 48fcbb9e-5639-0410-8b25-842128a4905d
Periods and components may be queried for underlying indices.

git-svn-id: http://svn.finmath.net/finmath%20lib/trunk@1339 48fcbb9e-5639-0410-8b25-842128a4905d
Added "none" as a day count convention (it will return always 1.0 as yearfrac).

git-svn-id: http://svn.finmath.net/finmath%20lib/trunk@1340 48fcbb9e-5639-0410-8b25-842128a4905d