Fix SearchPanes and SearchBuilder not pre-filtering data

[gotmoo]

fixes #11

This is my take on having SearchPanes and SearchBuilder handle a pre-filtered setup for editor.

1st, in editor.cs, expose the _GetWhere method internally:

/// <summary>
/// Apply the global Where filter to the supplied Query
/// </summary>
internal void GetGlobalWhere(Query query)
{
    _GetWhere(query);
}

Then in SearchPaneOptions, apply the filtering twice by calling the above function with the query:

var q = db.Query("select")
    .Distinct(true)
    .Table(table)
    .Get(label + " as label")
    .Get(value + " as value")
    .GroupBy(value)
    .Where(_where)
    .LeftJoin(join);
editor.GetGlobalWhere(q);

and again later:

var entriesQuery = db.Query("select")
    .Distinct(true)
    .Table(table)
    .LeftJoin(join);
editor.GetGlobalWhere(entriesQuery);

Similarly, in SearchBuilder:

var query = db.Query("select")
    .Table(this._table)
    .LeftJoin(_leftJoin);
editor.GetGlobalWhere(query);