Visit Scheduler

@dannyroberts @czue @millerdev - getting close to being done with this, feel free to start reviewing.

https://confluence.dimagi.com/display/ccinternal/Scheduler+Module?focusedCommentId=27365721&#comment-27365721

QA ticket: http://manage.dimagi.com/default.asp?125997

## Module View
![image](https://cloud.githubusercontent.com/assets/249606/3601314/48aacbee-0d00-11e4-9f08-1856c6731bda.png)

## Module view with error
![image](https://cloud.githubusercontent.com/assets/249606/3601294/16496dc2-0d00-11e4-82c7-8edb4a5c31d5.png)

## Form view
![image](https://cloud.githubusercontent.com/assets/249606/3601327/61701954-0d00-11e4-8cde-4c122bf004e3.png)

## Form view alternate
![image](https://cloud.githubusercontent.com/assets/249606/3601333/74159e9e-0d00-11e4-95ff-95d59c41d2ba.png)


What do you think about adding tests for this new XPath functionality (all the new and changed methods, not just this one)? I searched around, but didn't see them in this PR.