Add Soft Credit trigger and soft credit type condition

I was surprised to see that there were no triggers for soft credits in Civirules - and then I found out there were no pre/post hooks. So yesterday I added pre/post hooks and added support for Soft Credits to Civirules. To make it actually useful, CRM_CivirulesPostTrigger_ContributionSoft pulls in the associated Contribution data and I added a new condition of "Soft Credit Type is (not) one of".