* tests
  Stages `build' and `test' reinstated and working.
* Dockerfile
  Tweaks to make testing using `test' command operational.

* shiny-state.R (which_gui_inputs, which_metfrag_inputs,
unpack_app_state, unpack_app_state_metfrag, input2conf_metfrag,
input2conf, app_state2state): Updated. The inputs are defined
in a more structured manner and this resulted in having to update
the entire system of state creation fom GUI.

* shiny-ui-base.R : Updated. Temporary reorganisation while the
app.Rmd is being rebuilt.

* state.R(metfrag_param): New function. Creates MF parameter object.
(metfrag4conf): New function. Creates a conf entry.
(metfrag_conf): Updated.

* inst/rmd/app.Rmd: Under reconstruction.

* inputs_metfrag: New file.

DESCRIPTION: Depends: Add readxl and sort alphabetically. Change order of contributors to (mostly) alphabetical.

Last author is going to be the leader of the group, the first is the
most important contributor (author, creator).

* envopts.R: New file.

* DESCRIPTION: Update.

* errors: Replace variable error conditions with `check_' functions.

* man: Update.

* api: Update with new error variables.

* errors: New file to define error conditions.

* state (init_state, is_metfrag_available, new_runtime_state,
new_empty_project, new_project, ^.*_conf funs): Some updated, some
new.

* test-state: Update with tests for new functionality.

* DESCRIPTION: New version and doc engine.

* NAMESPACE: Adapted.

* man: Updated.