Extended the plugin system to allow for dynamic runtime bindings between modules.

As a test implementation, this allows the TablesPage to open a CrudTab for a table/view without
the need for TablesPage, CrudTab and DatabaseWindow to know anything about each other.

pglab/plugin_support/IPluginContentWidgetContext.h

@@ -0,0 +1,51 @@
+#ifndef IPLUGINCONTENTWIDGETCONTEXT_H
+#define IPLUGINCONTENTWIDGETCONTEXT_H
+
+#include <QString>
+#include <memory>
+#include "plugin_support/ModuleActionParameters.h"
+
+class OpenDatabase;
+class PluginContentWidget;
+
+/** This class serves to isolate the plugin from the actual construct in which it is
+ * used.
+ *
+ * It provides interface for operating on the context without needing to many details.
+ * Actual default implementation is in PluginContentWidgetContextBase.
+ */
+class IPluginContentWidgetContext {
+public:
+
+	virtual ~IPluginContentWidgetContext() = default;
+	/** Tells the context what to use as a caption for this content widget.
+	 *
+	 * Depending on the context the caption might not be visible or used as the caption
+	 * of a window or tab.
+	 */
+	virtual void setCaption(PluginContentWidget *content, const QString &caption, const QString &hint = {}) = 0;
+	/** Tells the context what icon to use.
+	 *
+	 * In general the icon is used in a similar place as the caption.
+	 * \param iconname Assumed to be the name of an iconresource. The system will look for different
+	 *   sizes under :/icons/<size>/iconname
+	 */
+	virtual void setIcon(PluginContentWidget *content, const QString &iconname) = 0;
+
+	/** Returns an OpenDatabase object the widget can use to access
+	 * the database.
+	 */
+	virtual std::shared_ptr<OpenDatabase> getDatabase() = 0;
+
+	virtual void showStatusMessage(const QString &msg) = 0;
+
+	virtual void moduleAction(
+			const QString &module_identifier,
+			QString module_action,
+			const ModuleActionParameters &action_params
+			) = 0;
+
+	virtual void addContentWidget(PluginContentWidget *widget) = 0;
+};
+
+#endif // IPLUGINCONTENTWIDGETCONTEXT_H