Update check_modules with HTML::Scrubber  line
Correct typos in Cosign.pm module
Move all problemLibrary configurations to defaults.config and localOverrides.conf.dist. Remove references in site.conf.dist

It was unnecessary and potentially confusing to do problemLibrary customization both in site.conf and in localOverrides.conf
Reduce the scariness of the warning messages about the extra published column which appears in older courses.
Improve completion message indicating that the upgrade process has been completed.
Update distributed configuration files
Merge pull request #64 from mgage/release/2.7

Updates to default configuration files
Merge branch 'release/2.7' of https://github.com/openwebwork/webwork2 into upgraded2.7
Fixing bugs in prepration for merge into master
- Backported add button bugfix for library browser
- Backported problemPreamble and problemPostamble buxfix
- Backported basic bootstrap integrationf or math3