[PLAT-6856] Stage 2: Remove deprecated related to obligor

This PR is a continuation of [REQS-666](https://opengamma.atlassian.net/browse/REQS-666), the item concerned is  [PLAT-6856](https://opengamma.atlassian.net/browse/PLAT-6856), which is to remove the rest of the deprecated methods from OG-Analytics and patch up the surrounding changes. This is the second stage of the sequence of patches required to do this, the first stage is in https://github.com/OpenGamma/OG-Platform/pull/271

The strategy used in removing the deprecated code is the same as that outlined in https://github.com/OpenGamma/OG-Platform/pull/262, please refer to it for details.

Some of the code not marked deprecated relates to CDS implementations that have since been replaced.