New features

Bug fixes:
Coding standards issue: #2764751
MixItUp Sorting Settings, has an invalid placeholder: #2850264

New features:
Filter tweak? : #2826729
Implemented ability to check only one checkbox and hide unselected items.
d8 / Type of filtering: #2874356
Added ability to select the type of filters widget: Selectbox or Checkboxes

This release contains the following bugfixes and features:
a509f3b Issue #2983849 by attilatilman: Error when saving a template mapping
27ace11 Issue #2977162 by Kova101: Supporting multiple GC field mapping to a single Drupal field with concatenation
5a44be5 Issue #2977159 by Kova101: Remove the upload module, because the API's next release won't support it
9d703a4 Issue #2948437 by Kova101: Exceeded max_input_vars for a single item
8a88e9f Issue #2856274 by Kova101, weri: Allow the selection of the text format to use for rich text fields

Development release.

This branch (3.x) MUST be used in conjuction with Registry on steroids.

Updated security. Added basic authentication.