Move documentationPath() from Core::ICore to Core::HelpManager

It is documentation related API, so it belongs there.

Change-Id: I5d1676f251e6deb92050ddedac19bf3c332aab54
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/coreplugin/helpmanager.cpp

@@ -30,6 +30,8 @@
 #include <extensionsystem/pluginspec.h>
 #include <utils/qtcassert.h>
 
+#include <QCoreApplication>
+#include <QDir>
 #include <QUrl>
 
 namespace Core {
@@ -67,6 +69,11 @@ Implementation::~Implementation()
     m_instance = nullptr;
 }
 
+QString documentationPath()
+{
+    return QDir::cleanPath(QCoreApplication::applicationDirPath() + '/' + RELATIVE_DOC_PATH);
+}
+
 void registerDocumentation(const QStringList &files)
 {
     if (checkInstance())