WebSubmit: autocompeltion for authors

* Provides an author autocompletion facility for WebSubmit. (closes #2276)

* The author autocompletion interface can easily be configured for each
  submission.

* Author sources can be defined as plugins that return results in JSON.

* Author submission and modification are fully compatible with existing
  BibConvert templates.

* Uses typeahead.js <http://twitter.github.io/typeahead.js/>
  for autocompletion.

Co-authored-by: Harris Tzovanakis <charalampos.tzovanakis@cern.ch>
Co-authored-by: Nikolaos Kasioumis <nikolaos.kasioumis@cern.ch>
Signed-off-by: Nikolaos Kasioumis <nikolaos.kasioumis@cern.ch>
69:19: E203 whitespace before ':'
106:1: E302 expected 2 blank lines, found 1
106: D203 Expected 1 blank line *before* class docstring, found 0
106: D204 Expected 1 blank line *after* class docstring, found 0
106: D205 Blank line missing between one-line summary and description
106: D208 Docstring is over-indented
121: D400 First line should end with '.', not '"'
121: D205 Blank line missing between one-line summary and description
121: D208 Docstring is over-indented
128:5: E301 expected 1 blank line, found 0
128: D400 First line should end with '.', not 'f'
128: D205 Blank line missing between one-line summary and description
128: D208 Docstring is over-indented
136: D203 Expected 1 blank line *before* class docstring, found 0
136: D204 Expected 1 blank line *after* class docstring, found 0
136: D205 Blank line missing between one-line summary and description
136: D208 Docstring is over-indented
154: D400 First line should end with '.', not '"'
154: D205 Blank line missing between one-line summary and description
154: D208 Docstring is over-indented
161:5: E301 expected 1 blank line, found 0
161: D400 First line should end with '.', not 'f'
161: D205 Blank line missing between one-line summary and description
161: D208 Docstring is over-indented
169: D203 Expected 1 blank line *before* class docstring, found 0
169: D204 Expected 1 blank line *after* class docstring, found 0
169: D400 First line should end with '.', not 'n'
169: D205 Blank line missing between one-line summary and description
169: D208 Docstring is over-indented
180: D400 First line should end with '.', not '"'
180: D205 Blank line missing between one-line summary and description
180: D208 Docstring is over-indented
187:5: E301 expected 1 blank line, found 0
187: D400 First line should end with '.', not 'f'
187: D205 Blank line missing between one-line summary and description
187: D208 Docstring is over-indented
195: D203 Expected 1 blank line *before* class docstring, found 0
195: D204 Expected 1 blank line *after* class docstring, found 0
195: D400 First line should end with '.', not 'n'
195: D205 Blank line missing between one-line summary and description
195: D208 Docstring is over-indented
203: D400 First line should end with '.', not '"'
203: D205 Blank line missing between one-line summary and description
203: D208 Docstring is over-indented
210:5: E301 expected 1 blank line, found 0
210: D400 First line should end with '.', not 'f'
210: D205 Blank line missing between one-line summary and description
210: D208 Docstring is over-indented
218: D203 Expected 1 blank line *before* class docstring, found 0
218: D204 Expected 1 blank line *after* class docstring, found 0
218: D400 First line should end with '.', not 'n'
218: D205 Blank line missing between one-line summary and description
218: D208 Docstring is over-indented
226: D400 First line should end with '.', not '"'
226: D205 Blank line missing between one-line summary and description
226: D208 Docstring is over-indented
233:5: E301 expected 1 blank line, found 0
233: D400 First line should end with '.', not 'f'
233: D205 Blank line missing between one-line summary and description
233: D208 Docstring is over-indented
240:1: E302 expected 2 blank lines, found 1
240: D203 Expected 1 blank line *before* class docstring, found 0
240: D204 Expected 1 blank line *after* class docstring, found 0
240: D400 First line should end with '.', not 'n'
240: D205 Blank line missing between one-line summary and description
240: D208 Docstring is over-indented
248: D400 First line should end with '.', not '"'
248: D205 Blank line missing between one-line summary and description
248: D208 Docstring is over-indented
255:5: E301 expected 1 blank line, found 0
255: D400 First line should end with '.', not 'f'
255: D205 Blank line missing between one-line summary and description
255: D208 Docstring is over-indented