Fix ASP.NET

Plaintext, JSON and database tests should all work except for the fortunes tests.

Had to downgrade to ASP.NET MVC 4. When mono is released with [these changes](https://github.com/mono/mono/pull/1163), we can upgrade to ASP.NET MVC 5.2.2 and the fortunes tests will also work.

When I launch nginx myself, everything seems to work. But `toolset/run-tests.py --mode verify --install server --test aspnet-mono` doesn't work for some reason.

```
vagrant@TFB-all:~/FrameworkBenchmarks$ cat results/ec2/latest/logs/aspnet-mono/out.txt
test.os.lower() = linux  test.database_os.lower() = linux
self.results['frameworks'] != None: True
test.name: aspnet-mono
self.results['completed']: {u'aspnet-mono': u'port 8080 is not available before start'}
```
Envvars are stored in the `mono.installed` file and the `.` loads them from the file. It's confusing at first but I think it beats copy & pasting 6 lines of exports in every file that needs them. If mono is installed, they will be there. If mono is not installed, then xsp installation will fail because you need mono to compile and install and run xsp.