Implement device IO as a shared library

Provide make targets and build configuration to create a shared object
for other systems/applications to use to control keyboard LEDs without
 the need for instantiating the g810-led process.

Provide make targets for installing library and development files into
environments, such as the current system or package builders.

Currently preserves precious behavior of building g810-led binary as
statically linked. Provides an alternative build target of "bin-linked"
which will create a dynamically linked variant.

Signed-off-by: Kevin Pearson <pearson.kevin.m@gmail.com>

INSTALL.md

@@ -38,6 +38,14 @@ Fedora :</br>
 `make` # for hidapi</br>
 `make LIB=libusb` # for libusb</br>
 `sudo make install`</br>
+`make install-lib` to install the libg810-led library.</br>
+`make install-dev` to install the libg810-led library and headers for development.</br>
+
+## Building the library :</br>
+The library is built by default when running the `make` (default target "all").</br>
+
+To specifically build the library as a standalone component: </br>
+`make lib`</br>
 
 ## Update :</br>
 Same as install, but your profile and reboot files are preserved.</br>