prevent duplication of alarms
the rule interfaces were rewritten every time a rule was opened for editing

this was of course raising an exception when two items' rules were open for editing, and the OK button was pressed in the previously-opened one
do not clean history when opening a database
don't store a fake root item (id 0) in core.items.items
sort occurrences in the interface
use JSON for storing item rules in the database
don't try to hide bad id type
store items in each database object
bugfix: history panel's sash not correctly positioned
replace logging extension with filters
make development extension much more dynamic
development extension: populate tree with different rules
log successful exit at info level
if -> elif
reorganize how menus are updated
development add-ons: improve print tables
don't try to cancel the timer when it's not alive
make it possible to suppress dialogs
rename core_api.get_items -> get_items_ids
let block database raise the Empty exception