Support PinTextData R/W

[ttimasdf]

09cb8bd Add preliminary support for reading PinTextData from SchLib. But the data is discarded after read out, nor saved when writing to file. Currently I'm adding a byte array field to SchPin to store the raw data. However, I don't know the meaning of it.

I reverse engineered AD KiCad Importer plugin (including the SDK dll with it) but not finding any useful components (regarding the binary file format). But this class looks close to it.

namespace KiCadLib.SCH
{
    internal class SchTextBase : SchItemBase
    {
        public SchTextBase()
        {
            this.Value = string.Empty;
            this.Orient = SchTextBase.Orientation.Left;
            this.Height = 0;
            this.Width = 0;
            this.Bold = false;
            this.Italic = false;
            this.Mirrored = false;
            this.HorizAlign = SchTextBase.HorizontalAlign.Center;
            this.VertAlign = SchTextBase.VerticalAlign.Center;
            this.Shape = SchTextBase.PinShape.Input;
            this.IsV6 = false;
            this.FieldsAutoplaced = false;
            this.Properties = new List<SymField>();
        }
    // ...