Support for easily building a faban tarball out of the box.

[jvirkki]

This addresses issue #47 (in akara/faban github repo).

A top-level build.xml is added which will build an installable tarball
by running ant with no options or configuration needed.

The changes to support this are:

• JDK location is obtained from $JDK_HOME environment variable. This removes
  the only required customization from the property files. JDK_HOME is
  a fairly standard env var so many java developers will have this set already.
• Instead of having to create a custom build.properties, each build.xml
  now includes both build.properties (which is not included in the source
  repository) and build-defaults.properties (which is the existing template
  renamed).
• Users who wish to provide local overrides for the build options can
  create a local build.properties file and override any options there.
  Because build.properties is loaded first, any values set there will
  override values in build-defaults.properties.
• Users who are ok with the defaults need to do nothing, defaults work as-is.
• The default nightly directory is set to be within the source tree instead
  of above it so faban build is self-contained by default.
• The build instructions in the README are updated accordingly.

[shanti]

Thanks for this Jyrri. I notice that you have renamed the build.properties.template and that is fine. But in the build.xml itself, you are including both the files: the user's build.properties plus the default file. Have you tested this with different values in 'build.properties' to make sure that overrides the default values?

[jvirkki]

Yes. The ordering matters there because in ant the first value given to a property will persist over any subsequent assignments. So here the build.xml includes build.properties first, which by default does not exist so that include is ignored and all the values set in the build-defaults.properties will take effect.

However, if a user creates a local build.properties it will be read first and those values will take precedence over anything in the defaults file.