BibIndex: centralisation of synonym treatment

* Removes CFG_BIBINDEX_SYNONYM_KBRS variable and moves the per-index
  synonym definitions to the database.  Adapts BibIndex Admin
  interface accordingly.  (addresses #852)

Co-authored-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: centralisation of stopword treatment

* Moves CFG_BIBINDEX_REMOVE_STOPWORDS to database to idxINDEX table.
  Adapts admin interface accordingly.  (addresses #852)

* Additionally, fixes a small bug for modifysynonymkb function
  in the BibIndex Admin interface.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Co-authored-by: Patrick Glauner <patrick.oliver.glauner@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: centralisation of LaTeX/HTML treatment

* Moves CFG_BIBINDEX_LATEX_MARKUP, CFG_BIBINXED_HTML_MARKUP
  to the database to the idxINDEX table.  Adapts admin interface.
  (addresses #852)

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Co-authored-by: Patrick Glauner <patrick.oliver.glauner@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: new regression tests

* Adds tests for remove_stopwords, remove_html_markup, remove_latex_markup.

* Refactors other tests in bibindexadmin_regression_tests.py.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: centralisation of tokenizers

* Introduces tokenizers for journal, year, fulltext and authorcount indexes.
  Merges old tokenizing functions for pairs, phrases and words into
  one 'BibIndexDefaultTokenizer'.  Introduces empty tokenizer.
  Extends admin interface to support tokenizers.  (closes #852)

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: pluginutils for tokenizers

* CFG_BIBINDEX_PATH_TO_STOPWORDS_FILE now is a
  CFG_BIBRANK_PATH_TO_STOPWORDS_FILE.
* Indexes have their own path to stopwords file.
* Tokenizers are loaded with pluginutils.
  (references #852)

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>