return some error message in global error handler

it is really bad practice for us not to return anything in case of
error. In \BlueLaTex,we always return an error message to briefly
explain what happened
extract configuration loader to own bundle

All bundles potentially use the configuration loader, and to avoid
cyclic dependencies, the best way to do it is to have a bundle whose
single responsibility is to register the configuration loader.
Thus, it will probably be the first bundle that is started and then
everybody is happy and can use it.
test new travis configuration
(hopfully) fix character escape
print potential errors after script execution
make couchdb instance optional
add license file
change return type

a `BlueLet` now returns any result, it is simply ignored, no matter
what. This mainly avoid to map the final `Try` object to make it return
unit.
add service to save a non synchronized resource
add service to retrieve a resource
add service to delete a resource
add service to unregister a user
update dependency versions

after new release of sohva and tiscaf, let's update the dependencies
delete references to unregistered user

If a user is single author for any paper, then he cannot unregister. He
must first either delete the paper data or give another user the author
role for this paper.
If everthing went well, delete references to user as author or reviewer
for all papers he plays a role in.
generate build information object

this object contains information about the current \BlueLaTeX version
being compiled, such as version, scala version, compilation date and time
make couchdb port configurable

Environments that use existing couchdb instance may disable custom server
starting and use a different port.
make tests more configurable
add tests for login/logout
add new tests for login/logout
improved test framework

 - make it possible have some predefined papers for a scenario
 - do not delete databases between runs, only delete non design
   documents