Improve integration with Bootstrap classes for 100% compatibility with Bootswatch

We tested different bootswatch themes (http://bootswatch.com/2/) using theme_easy (https://github.com/FMCorz/moodle-theme_easy). The following Moodle “elements” are not using Bootstrap classes, and so they look odds as soon as we switch from Clean to a different Bootstrap theme:
form elements
file picker
file manager
globally all the Moodle dialogues
crumbtrail would look better with most navbar-inverse css classes
course page: current week highlight
collapsible fieldset names

See bootswatch usage on the prototype: http://prototype.moodle.net/clean2/admin/settings.php?section=themesettingeasy