[IMP] sale,purchase: allow invoicing

(closes #500)

(cherry picked from commit 84c0595aef3a417702c81b5226ae1f61817a2bf8)
[FIX] sale: move menu to avoid error at install of website_quote

(closes #2728)
(cherry picked from commit 2b1e1e70dd537f02f776e58c9def195ecff839c5)
[ADD]Event: functionality of Event Mail Scheduler after subscription,before event and after event

[IMP]add access rule for event.mail and fix typo

[IMP]imporved code and labe

[IMP]updated cron job by 1 hour

[IMP]fix typo, apply group no one

[IMP]change onchange for one2many and set default value for boolean

[IMP]remove unused code

[IMP]add template for event mail schedule and test cases for the event mail scheduler

[IMP]indentation

[IMP]improve the code as per new api

[IMP]imporve the code for send mail

[IMP]improved sender mail in template

[IMP]improved sender mail in template

[IMP]fix variable declaration

[IMP]add domain for confirmed an done event.

[IMP]tree view editable and remove mail schedule technical group and add minute in interval

[IMP]set default value and imporve cron job function

[IMP]improvement according to new api.

[IMP]fix typo
[IMP]move multi currency to usability category