This readds the custom.css file to overwrite the default cloudstack styles.
Currently this is only possible by adding them to the custom.scss in the repository and compile them into the cloudstack3.css.
Now there is an empty custom.css created when compiling the scss source. This custom.css can be overwritten with the custom styles afterwards.
This functionality was broken by #3328.
* Introduce jsbeautifyrc and sass linter for automated unified scss code syntax
* Introduce new z-index scss file to manage different z-index correctly
* Use beautify tool for scss files and sass lint fix all scss files
* Add vscode folder to gitignore
* Add more new files to global gitignore
* Refactor scss files and rework custom styles implementation strategy
* Remove outdated ie7 styles
* Fix typo of facebook input token include
* Fix apache licences for new lint files
* Splitt massive cloudstack.scss into many modular and smaller files
* Refactor scss language files
* Change and move apache licence css file name
