Continue evaluation after non-fatal errors, and accumulate/display the errors, so that users can use the additional evaluated data (for hovers, references, etc.)

[harrisont]

Right now errors throw an exception and stop the evaluation. This issue is to instead continue the evaluating even after hitting non-fatal errors. This involves:

• Distinguish between fatal and non-fatal errors, and determine which each error is.
• Track the errors in the context.evaluatedData.
• Change diagnosticProvider.ts and server.ts to handle the multiple errors.