Add options for the log in settings

Related to #298 - Log app events to file

Changes:

[@stdevCrow] Add a friendly ComboBox to let the user choose between different log levels
[@stdevCrow] Add settings's properties logLevel and logOutput
[@stdevCrow] Add options inside Global Settings to select the log level and the log output
[@stdevCrow] Minor improvements over the general layout of the Address Book section
[@stdevAntiD2ta] Add function LevelFromEnum
[@stdevAntiD2ta] Add enum for log level (This function returns a logrus.level from an enum identifier)
[@stdevCrow] Remove duplicated aliases
[@stdevCrow] Set the logOutput property's type to int
[@stdevCrow] Add a new property logOutputFile, in order to allow having an output log file with any name (even stdout or none) without conflicts
[@stdevAntiD2ta] Add configuration option outputFile, related with the previous point
[@stdevCrow] Cast to integer the properties logLevel and logOutput

Comments about testing , should you have some

fibercrypto / fibercryptowallet