#274 inject custom assets

[Oleg Sverdlov]

We'd like to propose a feature that enables to inject custom assets (JS and CSS files) from a folder to header of every page. The assets folder's path is set via global conf.
Should call it “poor man's assets management" :)
We would appreciate a feedback.
https://github.com/matrix-israel/openemr/commit/d04ae45b15bf84f65f44ec73ebe4bba2c6b61839