JShint will be executed with paver run_jshint, which will use a defined set of
directories (likewise defined are directories to ignore). A limit can be imposed
on the total number of violations. Note that this change does NOT include adding
jshint to diff-quality or `paver run_quality`.

With the old logic, we weren't running pylint on openedx at all.  We
were also running it on lms/lib/comment_client twice, and on the
installed xblock third-party library.

Jenkins "Quality Report" pep8 output now lists all pep8 violations,
not just the number of violations.

We are not using the limit flag in the actual run_pep8 method; removing
that from scripts. Operationally, pep8 has been enforcing a limit of
zero for awhile; this finishes that realization.

Also, all pep8 reports now appear under the reports/pep8 folder, rather than
per-system.

This reverts commit 19c767eb.

This reverts commit 747756a9.

Move lms.lib.xblock into lms.djangoapps.lms_xblock in preparation add database backed configuration to it

Not on `paver run_pylint`

Leverages recent changes in diff-cover to reduce number of diff-quality runs

TE-555

When using -p, the underlying diff-quality command will pass that
number as a value for --fail-under.

For example,
  paver run_quality -p 75

Will pass 75 into the --fail-under switch on diff-quality.

Also upgrades diff-cover in order to take advantage of this funcitonality.

This adds the -l switch, wherein a violations limit is passed in. For
example:
  paver run_pep8 -l 700

Will fail if more than 700 violations are found.

By default, this limit is not enforced (i.e. if the -l switch
is not passed into the command, then a limit will not be put
into effect for that run)

This reverts commit 7fd2305f.