Refactor logging-related code out of util.{h,cpp} to a Logger class. A global logger object encapsulates the state. This will make it easier to add functionality to the logger such as syslog levels.
Related to https://reviews.bitcoinabc.org/T215.
Commits:
MOVEONLY: Move logging code from util.{h,cpp} to new files.
util: Establish global logger object.
The object encapsulates logging configuration, and in a later commit,
set up routines will also be moved into the class.
util: Move debug file management functions into Logger.
util: Encapsulate logCategories within BCLog::Logger.
util: Refactor GetLogCategory.
Changing parameter types from pointers to references and uint32_t to
BCLog::LogFlags simplies calling code.