Users can create a new .net SAM Application without directly using SAM CLI

[awschristou]

The existing "new sam app" functionality should work, but there may be some .net specific changes to make.

Acceptance criteria:

• User doesn't have to create files by hand
• User doesn't have to run commands at a command prompt
• User has a set of files produced for them that they can start working from
• appropriate .cs file is loaded into the editor after creation. If unable to determine a .cs file, open the template.yaml file instead

Appropriate .cs file = Try to load the .cs file referenced by the template.yaml file, if it exists, maybe falling back to something like Program.cs

[mpiroc]

Depends on #259 .

[mpiroc]

The only work for this task is to open the main code file after project creation. The rest is already implemented.