Not sure why I'm getting
```
Fehler beim Abfragen der Syncthing-Konfiguration: Error transferring http://127.0.0.1:8384/rest/system/config - server replied: Forbidden
URL der Anfrage: http://127.0.0.1:8384/rest/system/config
```
one one of my setups but this kind of error can likely be ignored shortly
after the start similar to other types of errors.
Apparently this is still problematic leading to errors like
`Qualifying with unknown namespace/class`. It seems that moving the enum to
a different header file works. The trick to use a macro to define
`enum class` ceased to work on the other hand.
Specifying a function with the namespace like
`void QtGui::FinalWizardPage::showResults()` leads to the same problem and
also needs to be avoided.
* Do *not* build Syncthing in addition as standalone executalbe
* Explose instead all of Syncthing's commands via the library
interface
* Make all of Syncthing's commands (including `serve`) accessible
via Syncthing Tray's executable
* Remove copied code for directory creation and instead use
upstream's code directly
* Do not blindly override existing auto start entry
* Warn if an auto start entry exists but points to a different executable
* Allow removing such an entry explicitly
* Avoid overriding argv/argc via `CMD_UTILS_CONVERT_ARGS_TO_UTF8` in
Windows-specific code when processing arguments from a 2nd instance
* Move the other startup code to main as well as they are not needed when
processing arguments from a 2nd instance
* Improve debug logging
* Use `waitForBytesWritten()` instead of `flush()` when passing args as
recommended by the documentation
* Avoid use of `bytesAvailable()` as it doesn't work as expected in this
situation on Windows (likely it doesn't really work reliably on all
platforms); calling `readAll()` works and is simpler anyways
* Tested that `--replace` works as well; also the
`waitUntilGone && QFile::exists(fullServerName)` block is entered and if
the previous instance is taking some time it really waits until it is
gone
Martchus