Expose build environment variables to notification templates

When running a build, Bamboo provides several variables that can be access by "${bamboo.sth}" based on the Bamboo Variables documentation.

The environment variables available to your job can be seen by adding a Script task with:

# if Windows, uncomment the following line by removing the hash (#) character
#set

# if Linux, uncomment the following line by removing the hash (#) character
#env

There are variables that are not exposed to the notification templates. An example would be a variable that holds the Build Working Directory (i.e.: ${bamboo.working.directory}).

Please, update the documentation by providing with a list of variables that are available to the notification templates.