Proper error handling in apiProxy
Add array func, fix empty rows in array_agg

array_agg returned [None] insead of [] if there were no rows
Fix reservation history migration (dt strings)
Adapted 'book single room' page

* Refactored BookingConfirm RH
* Splitted common elements in booking pages in several widget templates
* Refactored clientside validation
* Rendered repeatability/flexible days with WTForms
* Fixed holidays warning
* Fixed rendering glitch in RB calendar for single room
* Removed old template
* Added callback to timerange widget
* Minor style tweaks
Post-WIP fixes
Cleaned util JS functions

* Removed unused datetime validation
* Added go_to_room helper
Validation for reservation with days in advance