Add --props-file option to read properties during project generation

[romain-grecourt]

Users need to be able to generate projects using the properties file by using a new --props-file argument:

# generate first project
# anser questions etc.
helidon init

# generate 2nd project using the answers from the first project
helidon init --props-file my-project/.helidon

The props-file does not need to be the .helidon file. It can also mirror properties used with --batch:

./helidon init --batch -Dsecurity=true -Dapp-type=custom -Dflavor=mp

becomes

./helidon init --batch --props-file myfile.props

#myfile.props
security=true
app-type=custom
flavor=mp

See #690