The install instructions for "header only" refers to the wrong folder

Fix #2034

bin_to_hex.h: include spdlog.h 

remove std::distance usage

std::distance internally runs a loop, which may or may not be optimized
away. Just use simple arithmetic.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Ensure exported package is relocatable

As per CMake's Importing and Exporting Guide[1],
configure_package_config_file() should be used for configuring the
package configuration file, not the regular configure_file() function.

This ensures that a spdlog package built on one system (with a given
directory tree) can be imported from a different system -
e.g. creating a pre-compiled spdlog package for use on different
systems.

[1]: https://cmake.org/cmake/help/git-stage/guide/importing-exporting/index.html#id8

fix include file twice in the same file

Removal of C++14-specific std::make_unique from mongo_sink.h

Fixed typo in README

Added common class for all qt objects

Added factory funtion overloads for QTextEdit, QPlainTextEdit and QObject objects
cleaned qt_sink ctor

Removed separate class for qt_sinks and also send logs to any custom qt (QObject) classes (QML, QFile, custom Widget etc.)

Simplified Qt sinks

Trim the newline-chars instead of removing of 2 chars

Removed private class that derived from QObject

Removed private class that derived from QObject