NPE for included config with combined origins

[radist-nt]

1. Append file includedConfig.conf with the following content to the src/test/resources:

include "./asyncAppender.conf"
test.logback {
}

2. Modify file name in the first line of org.gnieh.logback.config.ConfigConfiguratorTest.testConfigureAsyncAppender() to includedConfig.conf
3. Run tests.

Expected results: passing tests
Actual results:

java.lang.NullPointerException
	at ch.qos.logback.core.joran.spi.ConfigurationWatchList.convertToFile(ConfigurationWatchList.java:93)
	at ch.qos.logback.core.joran.spi.ConfigurationWatchList.addAsFileToWatch(ConfigurationWatchList.java:59)
	at ch.qos.logback.core.joran.spi.ConfigurationWatchList.addToWatchList(ConfigurationWatchList.java:67)
	at ch.qos.logback.core.joran.util.ConfigurationWatchListUtil.addToWatchList(ConfigurationWatchListUtil.java:68)
	at org.gnieh.logback.config.ConfigConfigurator.lambda$2(ConfigConfigurator.java:342)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at org.gnieh.logback.config.ConfigConfigurator.registerFileWatchers(ConfigConfigurator.java:342)
	at org.gnieh.logback.config.ConfigConfigurator.configure(ConfigConfigurator.java:163)
	at org.gnieh.logback.config.ConfigConfiguratorTest.testConfigureAsyncAppender(ConfigConfiguratorTest.java:139)
...............

The problem is org.gnieh.logback.config.ConfigConfigurator.getSourceFiles(ConfigValue, Set<URL>). It's to naive to work as expected. The only valid way to gather files in current config library implementation is to provide the ConfigIncluder implementation to ConfigParseOptions.prependIncluder and pass the result to the one of ConfigFactory static methods.

[radist-nt]

Do you plan to publish a minor release with pull request #14 ?