ActiveProcess is not a Folder.

It became superfluous with commit 797a8c29.

To not receive catalog already tainted by clearing & reindexing.

In turn, this allows testing catalog reference content for equality:
catalog must be exactly the same before/after an ERP5Site_reindexAll, and
before/after a hot-reindex. So issubset is not an acceptable method.
Instead, use assertItemsEqual, and raise max diff size.

Also, tidy code a bit:
- Avoid clearing catalog only to restrict result set.
- Improve coding style.
- Simplify code (single-use variables...).
- Call assert methods producing more helpful error messages on failure.

And not the implementation detail of what type of activity may spawn in
the subsequent reindexation.

WARNING product/ERP5Form/ListBox.py:987 DeprecationWarning: Each line of the
"Sortable Columns" field property must be in the form "<column_id> |
<cast_type>", where <cast_type> is one of ('', 'float').

PublicHoliday_view

These are done through 'validate_action' not at 'validate' Workflow transition.

text_content_{error,warning}_message_list was properly set through
Component_modify Interaction (used for editing Component) which checks the
source code without raising an exception.

Half-broken, not useful after all and potentially harmful once Products
Documents will be migrated from FS.

* Use *Component temp_object instead of ad-hoc dicts (cleanup).
* Select 'version' for all the modules at once instead of per modules (not
  practical when migrating many modules, eg for migrating Products Documents).
* Fix naming of Form Fields (s/my_/your_/).

Only the current ListBox page was submitted because this simply doesn't work
with temp_objects. Instead, display all of the modules to be migrated on a
single page.

This can be chosen through Preference => "User Interface" tab. CodeMirror
default keymap is used by default as until now.

Before this change, expression_instance would not be set when expression is
modified, leading to either non-applied filter expression (when no
expression_instance existed) or use of an outdated expression.
Use a volatile attribute to store the expression: it does not change the
amount of work needed to load the Expression instance (pickle is the raw
python expression as text) and it remove data duplication in exported
documents.

This reverts commit fe84b799.
I did not intend to push that hash (copy/paste mistake).