Allow to submit without specifying solution file

[chocopowwwa]

This pr allows submitting exercism solution without specifying the actual solution file, I tried to implement this as suggested in https://github.com/exercism/cli/issues/824#issuecomment-563903452 and the previous comment.

Note: I haven't try all possible languages, I tried manually for bash and c, and my test cases only check for bash, c, cpp, crystal, dart, elixir, go, and haskell. Since this PR require some labor work (50+ languages that are active) to make sure all languages are supported, first I'd like to see some review of the code, if the code looks good then I'll continue to complete the test case.G

[arlm]

Isn't this already happening? I think the PR could be closed.

[ErikSchierboom]

This has been implemented.