Merge pull request #1617 from nabinhait/v4-hotfix

test case fixes
Merge pull request #1618 from nabinhait/v4-hotfix

Test case fixes for serial no
Merge pull request #1621 from nabinhait/v4-hotfix

BOM validation message fixed
Added hook: setup_wizard_exception
Merge pull request #1625 from anandpdoshi/hotfix

Added hook: setup_wizard_exception
added description to letter head in setup wizard
fixes frappe/erpnext#1627
4_0 patch dir renamed to v4_0
import, export and report permission in account and pricing rule
Merge branch 'develop' of github.com:frappe/erpnext into v4-hotfix