Spanish translation for the 3.12 release

Squashed commit of the following:

commit f81fc8f
Author: mgrojo <mgrojo@gmail.com>
Date:   Sat Feb 15 23:36:56 2020 +0100

    Some improvements to the Spanish translation

    - Do not use Title Case in Spanish as recommended by:
      https://es.l10n.kde.org/normas_generales.php
    - Consistency in references to GUI elements
    - Do not translate Shift since it has to match the official Qt translation
    and they seem to keep changing it in different versions. Leaving it
    untranslated, it is automatically translated when reference in GUI elements

commit 39b8470
Merge: d19a1b2 d393dd3
Author: mgrojo <mgrojo@gmail.com>
Date:   Sat Feb 15 21:39:50 2020 +0100

    Merge branch 'master' of https://github.com/lulol/sqlitebrowser into lulol-master

    Fixed some undefined entities.

    # Conflicts:
    #	src/translations/sqlb_es_ES.ts

commit d393dd3
Author: lulol <melus0@wanadoo.es>
Date:   Sat Feb 15 15:00:39 2020 +0100

    Updated Spanish translation

    It didn't like the 'iquest' entity for '¿' in the html block. Will try the UTF-8 version directly and try again.
    Used the new source 6683a9f

commit d6486b1
Author: lulol <melus0@wanadoo.es>
Date:   Sat Feb 15 14:42:53 2020 +0100

    Updated Spanish Translation.

    Trying again uploading the right file. :(

commit ec6883c
Author: lulol <melus0@wanadoo.es>
Date:   Sat Feb 15 14:36:48 2020 +0100

    Updated Spanish translation

    Fixed a formatting typo and consistency.

commit 851e3e2
Author: lulol <melus0@wanadoo.es>
Date:   Sat Feb 15 13:25:10 2020 +0100

    Updated Spanish translation