Add option to not read application.conf

[Tomasz-Zlamaniec]

c3p0 supports reading application.conf if TypesafeConfig is on the classpath.

In our use case Typesafe is required on the classpath but application.conf is not a valid "HOCON" file. C3P0Config.java reads application.conf in static initialization which always fails with an exception.

The exception is logged and the file is ignored but there should be a way of explicitly selecting which file should be used.