Admin console: issues with creation of system properties

Admin console doesn't currently verify the property's name when creating a system property. The creation will fail when it is sent to server, it should fail in the console itself, because console can verify if property's name is invalid. Server side failure should only occur when a property with the same name already exists.

Furthermore, it seems that in some scenarios, when you use an invalid name of a system property, for example containing some national characters, such as ěščžěščřěščř, the system property WILL get created (and will exist on the server), but the admin console will be UNABLE to show any of the existing system properties - when you navigate to system property page, it will show an empty table!!!! This will require deleting this property using CLI before system property management can be used in admin console again.

This also happens if the property's value has national characters.

NOTE: other than system properties, this applies to OSGi framework properties and most likely more property types as well.