Allow library manager to install JAR files to tools directory

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.

Start by tracing the library manager's handling of third-party libraries and the existing JAR placement flow for the tools directory and Tools menu. Define the installation boundaries and acceptance criteria for packaging both assets, including the security and code-signing questions raised in the issue.

Written by the indexing model from the issue text.