Feature flagged enrollment counts on instructor dashboard.

* enrollments counts removed from legacy dashboard
added tests for instructor_dashboard.py, added docstring for _is_small_course, removed check for settings.ANALYTICS_DASHBOARD_URL when creating dashboard link
Pylint: ignore TODO comments
Disable TODO comments in `paver quality` only
Disable FIXME errors on `paver run_quality`

Not on `paver run_pylint`
fixed quaility errors in instructor_dashboard.py, moved test_instructor_dashboard under tests/views directory
Set up validation_messages so that it goes through the RequireJS optimizer.
Simply check for existing text and type.
Clarify types of Python values.
Correct unresolved ugettext_lazy error strings in git_export command
Merge pull request #5910 from mitocw/cg/git_export_error_output

Correct unresolved ugettext_lazy error strings in git_export command
Prevent instructors from accidentally downgrading enrollment modes through instructor dash TNL-804
Fix PEP8: E201 whitespace after '{'
Fix PEP8: E202 whitespace before '}'
Fix PEP8: E203 whitespace before ':'
Fix PEP8: E211 whitespace before '('
Fix PEP8: E221 multiple spaces before operator
Fix PEP8: E222 multiple spaces after operator
Fix PEP8: E225 missing whitespace around operator
Fix PEP8: E226 missing whitespace around arithmetic operator