Fixes #1406 Recurring event date validation wrt start date

See merge request !708

deletion functionality for mass edition

fix #1349 and #1241 by adding deletion functionality to mass edition. It adds checkboxes for each field in the mass edit layout, which allows delete fields by just checking the checkbox without modifying the field contents.

![mass_edition_delete](https://code.vtiger.com/vtiger/vtigercrm/uploads/8209714be9f273bd405218414c5cdc1e/mass_edition_delete.gif)

See merge request !679

Fixes #1365 More popup drop-down in list actions

See merge request !707

Fixes #1397 Global search footer is fixed

See merge request !706

Fixes #1415 Our sites validation disable save button

See merge request !705

Fixes #1376 Email RelatedList Origin column renamed to Status

See merge request !704

Fixes #1433 Calendar view display mis-matches the dates from records

See merge request !703

Fixes #1438 Textarea fields data save

See merge request !702

Fixes #1409, #1410 Date range filter selection

See merge request !701

Fixes #1405 Recurrence event edit-view usability is addressed

See merge request !700

Fixes #1435 Deletion of calendar type won't work

See merge request !699

Fixes #1394 TaskManagement ui is broken

See merge request !698

Fixes #1360 List-view quick preview header

See merge request !697

showModal and showPopup one time registration is removed

See merge request !696

Fixes #1393 Related tabs comments ui

See merge request !695

Fixes #1367 Firstname with salutation is aligned

See merge request !694

Fixes #1370 Send,Save email modals

See merge request !693

Fixes #1373 Forward,Reply window default module

See merge request !692

Fixes #1428 Notify user of scheduled import status and email translations is addressed

See merge request !691

Fixes #1402 mentions without username

See merge request !690