Users should be able to set icons with the unicode ID too

[vladitasev]

https://openui5.hana.ondemand.com/test-resources/sap/m/demokit/iconExplorer/webapp/index.html#/overview/SAP-icons/?tab=grid&icon=accept

Icons from the icon explorer have a name and a unicode ID:

Some existing apps have user-defined content, where users have configured the icons by unicode IDs and not names. These apps need a way to support this with ui5-icon.

Add a unicode field to SAP-icons.json and allow passing the unicode ID as the value of the name property of ui5-icon.

[ilhan007]

It was decided not to support unicodes within the ui5-icon. Custom solution at stakeholder site would be planned and donee instead.