[IMP]hr,hr_holidays,hr_recruitment:improve usability point of hr_onboard...

...ing task add new toggle button widget for form view.

Task: https://www.odoo.com/web#id=10564&view_type=form&model=project.task&menu_id=3942&action=327
Pad: https://pad.odoo.com/p/r.zUPaUqErM8fV8bBJ

Here we move the datetime field to top of the form and put it on h2 tag in leave request form. the width of the datetime is 150px fixed so the time is hidden on datetime field to display time increase the width of textbox to 210px.
![trip with family - odoo 2014-12-29 12-33-21](https://cloud.githubusercontent.com/assets/7599718/5566723/59c322f8-8f57-11e4-952b-b4881cf78fa6.png)