Make availlable contributionTypeId and contributionTypeName to contribute message templates

When printing contribution receipts it is very useful to have information about the type of contribution
e.g. it can be added as additional information in the receipt
or different receipts can be printed depending if the contribution type is tax deductible or a membership fee, ...

the attached patch file provides the following two variables to the smarty template:
{$contributionTypeId}
{$contributionTypeName}