Adding MutableLines.update() and fixing popups

Using AppBase.onInputEvent()

Renaming the package org.luwrain.template to org.luwrain.app.base

LUWRAIN API update

README update

Fixing the bug with Selector.moveNext() and BrowserIterator.setPos()

Renaming src/tests to src/test

Adding associated object to Node and TextRun

Forgotten SectionsVisitor.java

DocTreeArea gets support of continuous reading