knowledge: PEP8 and PEP257 improvements

* Removes `__init__` methods.  (PR #2184)

Co-authored-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
workflows: passed data check

* Adds a check that passed data to the workflows API is indeed
  a list.

Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
workflows: wrong default position

* Fixes the default position of workflows when restarting a
  workflow.  (closes #2177) (PR #2186)

Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
linkbacks: fix tab visibility if excluded

* Adds module to excluded packages and disables tab in detailed record
  view.  (closes #1707)

* NOTE Adds deprecation warning for linkbacks module.

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
oauth2server: redirect uri validation fix

* Fixes security issue where redirect URIs was not correctly validated
  against the values provided by the client. (closes #2175)

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
legacy: fix form file attribute

* Addresses issue with missing legacy `file` attribute in form fields.
  (closes #1900)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
base: fix missing default config value

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
sqlalchemy: addition of Encrypted column type

* Adds submodule `types` inside `invenio.ext.sqlalchemy` package.

* Refactors the `types.py` into separate packages.

* Adds of a type named `Encrypted` that will be used for
  encrypting and decrypting `access_tokens`.  (PR #2173)

* Adds of pycrypto>=2.6.1 to `setup.py`.

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
restful: pagination fixes

* Refactors the `restful_pagination` file.  (closes #2102)

* Simplifies `link_header` method when concatenating links into
  one string.

* Renames file `restful_pagination` to `pagination`.
  (addresses #1724)

* Improves PEP8 and PEP257.  (PR #2087)

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
messages: general refactoring, fixes and improvements

* General refactoring and improvements including methods cleanup,
  API additions, oauth fix in REST, docstrings fixes.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>