[Win32 Builds] More VS2013 project changes for building PVR addons together with XBMC

This PR makes further Visual Studio project setting changes that make including the PVR projects in the main XBMC solution on windows easier.  It is a follow on from #333 where @wsoltys indicated he supported this goal of making it easier for PVR developers to debug/build addons within the main XBMC solution.  

If this PR is accepted, developers simply need to perform one action in the XBMC solution and they then have a fully functioning dev environment to build/debug/deploy PVR addon code from within the XBMC solution


The 4 changes in this PR are split on individual commits for easier review.  Let me know if they need to be squashed before accepting or whether they are OK as is.

- PostBuild event added to each pvr addon project that copies the addon deliverables into the XBMC solution addon folder, that ONLY runs when part of the XBMC solution (has no impact when part of the xbmc-pvr-addons solution)

- README update to remove information about the developer setting up their own post build events, since they are now there for all projects out of the box

- (tidy up) the xbmc-pvr-addons solution file had not been updated to VS2013 eventhough the vcxproj had been

- MythTV pvr addon would not work when added to XBMC solution due to a duplicate conflic with "libcmyth" project from PVR addons vs "libcmyth_dll" project in XBMC.  The issue is that although the XBMC project is renamed to "libcmyth_dll" the actual vcxproj was still left as "libcmyth.vcxproj".  This causes a duplicate warning ahd the pvr solutions libcmyth project cant be imported into the XBMC solution.  Not wanting to change anything on the XBMC side for this, I have renamed the projectname, projectfilename of the libcmyth project to libcmyth_pvr (note that the name of the produced library and any namespaces etc are not changed).  It is then succesfully able to be imported into the main XBMC solution.  I have verified that builds succeed in both solutions, and was able to enable the mythTV addon without any dependency/load errors (I do not have a backend so cant actually test the functionality).  I dont think this rename of project name/file should have any impact but would be good for @wsoltys @fetzerch and anyone else to please review this part of the change.  Im also not sure whether anywhere else would have a reference to this project name (eg does Jenkins build use the VS solution or something else?)

The first 3 changes are what was agreed on the previous PR so I dont anticipate any contenion there, but lets have some review/discussion about the libcmyth change I've made...  
I wanted to achieve the stated goal for all PVR addons (not just the one I work on), so rather than leave mythtv off the list, I thought this modification of filename/projectname only was surgical and low risk and any problems should be evident at build time, I dont think there are any runtime impacts

Additional pokes: @opdenkamp @FernetMenta @xhaggi @krustyreturns