Container init should fail with an more explicit message if .csproj cannot be located

[ArnaudBrousseau]

The following message is really hard to spot unless you know where to look (in docker logs, which you have to explicitly enable) and what to look for:

dotnetcore/2.0.5/init_container.sh

Line 34 in 7bc7c1b

echo Could not find .csproj or .dll. Using default.

I spent a fair amount of time chasing down why my app wasn't starting properly on Linux despite "successful" deployment. It turned out to be because the .csproj wasn't at the root of my git directory.

Changes proposed:

• Make the message more explicit. Something like "Could not find your .csproj or .dll in /home/site/repository/"
• When a .csproj isn't found, abort/fail with the more explicit version of the message. I'm not sure that it's desirable to silently fallback to /home/hostingstart/hostingstart.dll. If it's a must-have to fall back to this default dll, then fine to let this item go: displaying a more explicit message is already a win
• Icing on the cake: display a warning if multiple .csproj/.dll are found in /home/site/repository. Something like "[WARNING] Found multiple .csproj or .dll files in /home/site/repository. Using the first one on the list (head -1)"

[patricklee2]

we now use oryx to detection