…ptions

Previously, we forced the use of exceptions. Now users can easily toggle
the behavior. The default will still be to use exceptions for the safety
of new users, besides the added convenience.

**Usage:** set `dss_sharp.Error.UseExceptions = false` to deactivate the
automatic mapping. Other toggles as `Error.EarlyAbort` and the upcoming
`DSS.CompatFlags` should be enough to more closely match the logic of
older programs using the official COM DLL behavior even for the more
lax usage of OpenDSS.

Closes #15

- README.md: tweaks and pt-BR version.
- csproj: Add README.md as PackageReadmeFile, add licenses
- examples: add sample WinForms app and some notes, images
- add a dss_sharp.targets for copying native DLLs when building framework projects

- Use DSS C-API 0.13.3
- Add DSSCompatFlags.SaveCalcVoltageBases
- Port the comment about WdgCurrents/Voltages and open terminals

… and enums.