Add state and signal to catch the following two known problems:
* Linux: inotify user watch pool is exhausted. Folder watcher becomes
unreliable.
* Windows: buffer is too small, some notifications are lost but watching
stays reliable.
Use qCInfo for anything that has general value for support and
development. Use qCWarning for any recoverable error and qCCritical
for anything that could result in data loss or would identify a serious
issue with the code.
Issue #5647
This gives more insight about the logs and allow setting fine-tuned
logging rules. The categories are set to only output Info by default
so this allows us to provide more concise logging while keeping the
ability to extract more information for a specific category when
developping or debugging customer issues.
Issue #5647
