Read build properties from a file

[dylanmei]

When creating a new build, we should be able to fetch build properties from a Java/Groovy properties file. Add a new argument to build new, something like:

ht build new myProject myWorkspace property-file=file://myProperties.properties

[dylanmei]

This is added in c2a0df2.

ht build new --properties-file ../some.properties myProject myWorkspace