feat(Accounts): Add Condition Field In Pricing Rule

[abhishekbalam]

Condition field to add conditional expressions like in Assignment Rule:
territory == 'India' and order_type != 'Maintenance'

All fields available in the transaction (like Sales Invoice, Sales Order etc) are available
as their fieldnames directly for use in the conditions.

[abhishekbalam]

@rohitwaghchaure @deepeshgarg007

Docs Link:
frappe/erpnext_documentation#130

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed within a week if no further activity occurs, but it only takes a comment to keep a contribution alive :) Also, even if it is closed, you can always reopen the PR when you're ready. Thank you for contributing.

[abhishekbalam]

Will write and push tests today itself.

[deepeshgarg007]

@abhishekbalam any updates on this?

[abhishekbalam]

@deepeshgarg007
Will do this asap, I'm having bandwidth issues.

[abhishekbalam]

@rohitwaghchaure @deepeshgarg007

Test for condition field added.

[abhishekbalam]

Hi, requesting review since this PR is open for too long:
@nabinhait @rohitwaghchaure @deepeshgarg007