Cleaned up directory structure a bit

Moving the default theme from the ~/Content base directory to the
~/Content/themes/base dir
Include JS and styles as bundles

use bundles to minimize the files and http requests.
New jquery files

New versions of jquery and jquery ui
stuff
removed add set and add exercise

removed (unfinished) implementations to add an exercise or add sets to a
session. Will implement feature at later stage (maybe).
make use of bundles

include script and style bundles instead of adding every file explicitly
fixed issue #4

the each-loop in the next() and previous() method were not correctly
terminated when the correct session was found.