check if JDK's tools.jar is in the classpath

[monperrus]

in Dynamoth, check at startup one JDI class is available (eg Class.forName(com.sun.jdi.value)) and if not display an error message "add tools.jar in your classpath"

[monperrus]

Today, to build Nopol had to add the path to tools.jar as follows

        <dependency>
            <groupId>com.sun</groupId>
            <artifactId>tools</artifactId>
            <version>1.6.0</version>
            <scope>system</scope>
            <systemPath>/home/martin/martin-no-backup/jdk1.8.0_40/lib/tools.jar</systemPath>
        </dependency>