* Add support for placeholders in Config
Fixes#2870
* Replace placeholders only in logging config.
Placeholders in log level and filename incase of file output are replaced.
* Add Provision to filewriter module for replacing placeholders
* logging: Initial implementation
* logging: More encoder formats, better defaults
* logging: Fix repetition bug with FilterEncoder; add more presets
* logging: DiscardWriter; delete or no-op logs that discard their output
* logging: Add http.handlers.log module; enhance Replacer methods
The Replacer interface has new methods to customize how to handle empty
or unrecognized placeholders. Closes#2815.
* logging: Overhaul HTTP logging, fix bugs, improve filtering, etc.
* logging: General cleanup, begin transitioning to using new loggers
* Fixes after merge conflict
Sarat Chandra