Allow library manager to install JAR files to tools directory

[alexhutnik]

When developing 3rd party libraries, it is sometimes handy to have some 3rd party tools (i.e. available via the Tools menu). It would be nice if there was a way to package a tool along with its associated library and have both assets install to their respective locations.

Some questions to think about:

1. Security of including 3rd party JAR files in Arduino install
2. Will this interfere with code signing on, for example, recent versions of OS X
3. Right now the current mechanism when installing a 3rd party tool is to have the user download a JAR file and then place it in the tools directory in a particular way so that it is picked up by the IDE. Maybe this process could be improved upon? Perhaps a dialog box that asks for a URL and the user simply pastes a string that is fetched, unzipped, and installed.