Move NER tools logic into util

NER Libraries logic has been moved from its NERAdapter Actors to classes inside
the util package. This way, we can reuse that same logic when searching
(because it will require normalization of user input) without hesitation.
Change EUtils object to a class

The EUtils object has been changed to be a class, since a better design is
achieved this way. Also, its constructor is private-hidden and it can only be
constructed via its companion object factory, so previous "EUtils" calls can be
replaced with just "EUtils()" and will work the same way.
Add JSON mappers to all entities

Json Mappers (Play's Reads and Writes) have been added to all entities classes,
to easier transform them to JSON when returning them to a client.
Big cleanup and refactor of codebase

This is a big commit, lots of changes have been done here.

First: DAOs have been removed, allowing all code to directly work with the
TableQueries of Slick, since they are always more powerful that whatever
abstraction we can create over them; and, moreover, DAOs were a clean way to
work whenever only simple CRUD operations were involved, but when complex
queries were required, creating DAO methods over them became an ugly fucking
mess. And yes, we lose the abstraction over Slick and make all code dependent
on it, but that is a price that I am willing to take.

Second: Annotators have been split up into the Actor logic and the
Entity-Recognizer/Normalizer logic. The Recognizer/Normalizer has been put into
Service classes, and the Actor logic has been kept in the Annotator classes.
This way we can seamlessly reuse the Service classes to perform normalized
searches (say: earch for "boy", but recover anything that means the same, "homo
sapiens", such as "human" or "person"). Those services were previously placed
into the "utils" package, now they are in the "services" package.

Third: ScalaCheck has been placed as a test dependency, and with that and the
ScalaTest helpers for it, lots of tests have been cleaned up by using
generators and "forAll" checks.
Update ucc maven repository URL
Drop support for JDK6 in Travis

JDK6 is not supported by this project, since java.nio.file is being used, and
that was introduced in JDK7. That lack of support is causing, obviously, Travis
to fail its build when using openjdk6. So, just remove it.

Also, AnnotatorBaseSpec in annotator package tests has been removed and
replaced with ActorBaseSpec in the top-level package, that way we can reuse it
in some more Actors outside of the annotator package.
Add SearcherAdapter and implementations

A SearcherAdapter trait and implementation classes using the ABNER, Oscar and
Linnaeus services have been added into the searcher package. All of them
(implementations) perform a normalization of the search terms and just return a
set of keywords (by searching in the database) that match that normalized
terms. Also, a SimpleSearcher implementation has been added, that does not
perform any normalization, and just search for the Keywords in the original
texts of Annotations in the database.
Implement DocumentStatsService

DocumentStatsService is an Akka Actor that calculates statistics on (Document,
Keyword) pairs and stores that results into the DocumentStats table of the
database. It is configured in the Global Settings (see 'Global.scala') to perform
that statistics computation between some intervals (configured in
'conf/stats.conf').

Currently, statistics performed are based in counting the number of appearances
of a Keyword in a Document, and calculation of a ratio of appearance by
dividing that number with the total appearances of that same Keyword in all
documents.
Implement Searcher and Account entity

Searcher is the top-level searcher, it's responsibility is to communicate with
all enabled searchers in "conf/searchers.conf" to retrieve a Set of Keywords
which it will use to obtain the Documents that have any match with the received
search terms. It will also sort those documents based on the stats computed by
the DocumentStatsService actor, and stored into the DocumentStats database
table.

Also, an Account entity and an Accounts table have been added. These will store
the accounts of the system. We will only want to have administrator accounts
right now, so no worries about permissions or role-based authorization: if a
user is logged in, then it is an admin (no other possibility at the moment),
and it can do whatever it wants.