Move entityscore helper functions to new file

The entityscore helper functions were moved to a new file, because the
old file was named es.py and the file es.py will be used for
elasticsearch functionality.
Add module for elasticsearch functionality

Added a module for elasticsearch functionality to the entity_vis app.
The next step is to add a url mapping and a view for displaying the
frequency with which entity category words are used.
Add url mapping and view to display entity words

Added an url mapping and a view to display entity words and their
frequencies.
Add html template to display entity words
Show most frequent entity words per year

The entity words view and template were updated to show the most
frequent entity words per year (histogram).
Display entity word frequencies per genre
Show # of texts for entities per year
Display entity word frequencies by genre/year
Show empty page if no categories are set

The entity_words page displays frequencies of entity words. The entity
categories to display frequencies for are set in the get parameter
categories. If this parameter is not set, the page now shows an empty
page instead of an elasticsearch error.
Manage javascript packages using bower

For convenience, javascript packages are now managed with bower
instead of manually. A bower.json file was added, and the
bower_components directory was added as a static directory for Django.
Also the manually placed D3 package was removed and installed with bower
instead.
Add management command to print a list of available texts

Added a management command that prints a list of ids of titles whose
text is available in Nederlab/DBNL. The command takes an input parameter
specifying a list of titles in Nederlab/DBNL. The command filters this
list by checking whether a title is a play (genre drama) and the year is
in the right time period.
The next step is to also include titles via title.contains, to find
newer publications of old plays.
Add more titles using title.contains

Titles that contain exactly one work from the relevant time period are
added to the title list as well. We still need to find a way to handle
titles that contain multiple titles.
Add AngularJS
Move base template to general purpose template dir

A new general purpose directory was created to store project level
templates in. The base.html template was moved to this directory. This
was done as preparation of turning the Django application into an
AngularJS app.
Add bootstrap (and jQuery)
Add url mappings and views for browsing entities

Added url mappings and views for:
- browse_entities
- requesting entity categories (to specify what should be visualized)
- generating data about word pairs for a fixed set of entity categories
Fix entity_vis index template

The index.html template of the entity_vis app did not work anymore,
because D3 was moved to the bower_components directory. Fixed this error
by changing the path to d3.min.js.
Add Angular app for browsing entities

First step of an Angular app for visualizing information on entities.
- get entity categories from elasticsearch
- filter entity categories
- select main category and categories to combine the main category with
Add all titles using title.contains

The find_texts command now also checks whether titles contained in the
list of available titles are of genre drama and come from the right time
period. If so, the available title is added to the list of titles to
request. Sometimes a title has multiple versions in the relevant time
period, so doubles are added. They must be removed later.
Add additional year format to recognize

Sometimes the year field of texts contains a string like '17de eeuw'.
The command now also includes these years (for the relevant time
period).