Fix HTMLparser document upload

During a b2share deposit, and metadata submit, I received the error listed below.

It appears `HTMLparser` dependency is missing, and Invenio is using it's local [htmlparser](https://github.com/EUDAT-B2SHARE/b2share/blob/master/invenio/legacy/webalert/htmlparser.py) file incorrectly. I've renamed `htmlparser.py` to `htmlparser_local.py` and added the dependency.

```
Traceback (most recent call last):
  File "/home/vagrant/.virtualenvs/b2share/src/b2share/invenio/ext/legacy/layout.py", line 112, in <module>
    from invenio.legacy.webalert.webinterface import WebInterfaceYourAlertsPages
  File "/home/vagrant/.virtualenvs/b2share/src/b2share/invenio/legacy/webalert/webinterface.py", line 27, in <module>
    from invenio.legacy.webalert import api as webalert
  File "/home/vagrant/.virtualenvs/b2share/src/b2share/invenio/legacy/webalert/api.py", line 36, in <module>
    webalert_templates = invenio.legacy.template.load('webalert')
  File "/home/vagrant/.virtualenvs/b2share/src/b2share/invenio/legacy/template.py", line 112, in load
    ["invenio.templates.%s" % (module)])
  File "/home/vagrant/.virtualenvs/b2share/src/b2share/invenio/legacy/webalert/templates.py", line 31, in <module>
    from invenio.legacy.webalert.htmlparser_local import get_as_text, wrap, wrap_records
  File "/home/vagrant/.virtualenvs/b2share/src/b2share/invenio/legacy/webalert/htmlparser_local.py", line 23, in <module>
    from HTMLParser import HTMLParser
  File "/home/vagrant/.virtualenvs/b2share/src/b2share/invenio/legacy/webalert/htmlparser.py", line 23, in <module>
ImportError: cannot import name HTMLParser
```