Handle VersionlessFeatureException returned from binary scanner

[TrevCraw]

While user specified versionless features are not supported, the generateFeatures goal needs to be able to handle the VersionlessFeatureException that can be returned from the binary scanner. For now, we should catch the exception and display a message to the user about versionless features not being supported.

[turkeylurkey]

Added the feature "servlet" to server.xml <feature>servlet</feature>. Current message is:

[ERROR] Failed to execute goal io.openliberty.tools:liberty-maven-plugin:3.12.1-SNAPSHOT:generate-features (default-cli) 
on project demo-devmode-maven: Failed to generate a working set of features. Error scanning the application for Liberty 
features: com.ibm.websphere.binary.cmdline.exceptions.VersionlessFeatureException: CWMIG12156E: Versionless features 
are not supported. Specify a version for the servlet feature. -> [Help 1]

Note the sentence: "Specify a version for the servlet feature."

[turkeylurkey]

If there are multiple versionless features the binary scanner picks one to display in the message. Binary scanner picks the first version in the list and the list is generated by ServerFeatureUtil.getServerFeatures().

[TrevCraw]

Proposed error message:
"
If you would like to continue using auto-generation of features, please remove all versionless features from your server configuration. If you would like to continue using versionless features, you can turn off auto-generation of features by using the g hot key to toggle off auto-generation of features.
"

Need to figure out different message for standalone vs dev mode.