mention use of other open source code in readme

We use code from several open source projects to assist us, the licenses of that code & a link to the original code location is located in the headers of those java files
refactor some installer, and analytics code to better packages/classes
add 2nd analytics setup for new analytics server
make sure to refactor installer stuff inside offline dialog
CHANGED: parse and use warning message from modpack.xml
ADDED: more scrollbar fixes

 * Try to scroll textupackpane and map pane scrollbars to top