Allow pom-resolve to write the classpath to a variable-location.
Allow pom-resolve to write the classpath to a variable-location.

Pom-resolve already supported dumping the classpath to txt and to
json. This allows the user to specify a location for the txt file,
which previously went directly to .pants.d (a weird place to put
user-facing output). The api for this option matches what was
already offered by the json.

This also moves the printlns to be logger.info calls. That means
that vanilla pants runs won't print this information to screen
by default unless they have the appropriate logging output enabled.

(sapling split of 18968637ec35d2579623df7036fd1d9320861369)
foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio