shared: SandboxedProcessor: Perform MIME-type detection

Detect mime types, and for text/*, run the default text processor.

The added benefit is that we can now add plaintext files without extensions,
or many other text files (e. g. source code).

shared/sandboxedprocessor.h

@@ -1,12 +1,14 @@
 #ifndef SANDBOXEDPROCESSOR_H
 #define SANDBOXEDPROCESSOR_H
 #include <QString>
+#include <QMimeDatabase>
 #include "pagedata.h"
 
 class SandboxedProcessor
 {
   private:
 	QString filePath;
+	QMimeDatabase mimeDatabase;
 
 	void enableSandbox(QString readablePath = "");
 	void printResults(const QVector<PageData> &pageData);