* Schematic reference object now completely encapsulated.
* Schematic reference list object refactoring complete.
* Make OK default button in PCBNew block operation dialog.
Eeschema: cleaning code. Start work to enhance annotation algorithm.
Already added an option to annotate using sheet number (sheet 1 uses numbers 100 to 199, sheet 2 uses 200 to 299..).
Works fine if deleting existing annotation, but needs work to be used when the existing annotation is kept .