SCHEMA-808. Eliminate Maven profile named "profiling".

 - Replace the Maven profile with an always-on profiling Maven module
   that produces an artifact named kiji-schema-profiling.
 - Update enable/disable-profiling shell scripts to the new artifact file names.
 - Remove custom build script made unnecessary.

issue: https://jira.kiji.org/browse/SCHEMA-808
review: https://review.kiji.org/r/1904