Bug fixes and improvements

Fixed command line options (no duplicates, correct escaping and using single-dash instead of double-dash as the latest jdeps requires)
Fixed java toolchain support
Bound to verify phase by default for bound executions
Fixed logging
Bound mojo parameters to system properties that can be specified on command line
To make sure it does not [even inadvertently] use any API that is only available in java8 or later. Language features are controlled separately by {{javac}} and {{maven-compiler-plugin}} through {{-source}} configuration parameter, therefore in the current configuration it won't be able to use lambdas or any other fancy stuff from java8. But {{-source}} does not protect from using the incompatible API.