Interim synchronization with internal repository

This is an intermir commit to share what is going on with the development of the new /delta version.
Added instructions on how to develop /delta locally without a running backend
Updated developer instructions for enabling automatic login with url parameters.
Fixed Proxy configuration for development environment to be in read-write mode.
Implemented card archiving, both the DataModel login and UI (still very rough, though)
Improved tag handling.
Further improvements in tag handling and rendering
Improved tag handling

Now tag counting reflects whether archived cards are shown or not.
Also available the option to select all untagged cards, with matching counter.
Card deletion is now broken, while I found a way to handle the confirmation dialog (see DialogBox component)
Implemented the dialog to ask for confirmation when the user ask to delete a card

No keyboard shortcut implemented, yet
Improved Async logging in case of deferred being cancelled
Disabled watchdog in the proxy script
Added new version of React library
Initial draft of card editing mode

Still very early draft with tons of issues still to address, and no styling at all.

Disabled CSS preprocessor, due to limitations in Python SCSS processor.
Updated date Copyright notice.
Fixed a problem when reverting changes on a Record involving adding/removing fields.
Improved implementation of Record.Version
Fixed an issue when editing a card label (without tags)
Implemented "Clone card" command.
Added test highlighting a missing feature

Added a test to show that current implementation of 'cloneRecord' does not process DirectLogins yet.
Added a test to verify that 'cloneRecord' will fail when there are already pending changes.
Added the mask to avoid switching card, when in editing mode.