logic: handle java not found on windows and mac

* implemented java will not be used if it is not found on system
* add jni libraries weak linked for Mac
* use dlopen for lazy library loading
* added java path to preferences

src/lib_gui/qt/element/QtLocationPicker.cpp

@@ -41,6 +41,11 @@ void QtLocationPicker::paintEvent(QPaintEvent*)
 	style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
 
+void QtLocationPicker::setPlaceholderText(QString text)
+{
+	m_data->setPlaceholderText(text);
+}
+
 QString QtLocationPicker::getText()
 {
 	return m_data->text();

src/lib_gui/qt/element/QtLocationPicker.h

@@ -15,6 +15,7 @@ public:
 
 	virtual void paintEvent(QPaintEvent*) override;
 
+	void setPlaceholderText(QString text);
 	QString getText();
 	void setText(QString text);
 	void clearText();