Passing parameters to transactions
==================================

Arbitrary parameters can be passed to transactions by setting the *params* 
attribute when declaring the transaction. This feature is handy to re-use the
same transaction code for multiple calls but with different parameters.

A basic example:

    db._executeTransaction({
      collections: { },
      action: function (params) {
        return params[1];
      },
      params: [ 1, 2, 3 ]
    });

The above example will return *2*.

Some example that uses collections:

    db._executeTransaction({
      collections: { 
        write: "users",
        read: [ "c1", "c2" ]
      },
      action: function (params) {
        var db = require('@arangodb').db;
        var doc = db.c1.document(params['c1Key']);
        db.users.save(doc);
        doc = db.c2.document(params['c2Key']);
        db.users.save(doc);
      },
      params: { 
        c1Key: "foo", 
        c2Key: "bar" 
      }
    });