improve logging & reporting

[mahibi]

The log handling of the talk app needs to be improved.

current situation

• the Log util from android itself is used but there is no chance to get these logs from a user who wants to report a bug.

• the class "LoggingUtils" exists which obviously had the goal to have another logging with the possibility get the logs as a log file. (But unfortunately this flooded the logfile which led to bug reports like Log is flooded with errors while offline #1013).
  So the class can be considered experimental.

requirements

• there needs to be one solution for logging.
  • this might require to wrap the log commands from the android logging util?
• all logs should be written to a file
• use some file rolling strategy
• the user should be able to send the log file to nextcloud by mail (might require some research regarding file permissions)
  • before sending:
    • it might be useful to collect some information from the used nextcloud instance (server version, talk version, ..?) and append this to the log?
    • there must be the possibility to for him to scroll through the file and check if he has privacy concerns.
    • He has to confirm that all data from the file can be seen by nextcloud employees.
• the user experience for sending log files should be the same as for the files app (to be discussed with @tobiasKaminsky )
• as a first important usecase for improved logging it makes sense to concentrate on notifications

the logging solution from the files app might give some inspirations:
https://github.com/nextcloud/android-library/blob/master/src/main/java/com/owncloud/android/lib/common/utils/Log_OC.java

[mahibi]

when working on this issue, also have a look at the "exception" module from https://github.com/stefan-niedermann/nextcloud-commons