[minor] added currency in Totals for Trial Balance report

[mbauskar]

ERROR Report

Traceback (most recent call last):
  File "/home/frappe/benches/bench-2017-05-09/apps/frappe/frappe/app.py", line 55, in application
    response = frappe.handler.handle()
  File "/home/frappe/benches/bench-2017-05-09/apps/frappe/frappe/handler.py", line 21, in handle
    data = execute_cmd(cmd)
  File "/home/frappe/benches/bench-2017-05-09/apps/frappe/frappe/handler.py", line 52, in execute_cmd
    return frappe.call(method, **frappe.form_dict)
  File "/home/frappe/benches/bench-2017-05-09/apps/frappe/frappe/__init__.py", line 907, in call
    return fn(*args, **newargs)
  File "/home/frappe/benches/bench-2017-05-09/apps/frappe/frappe/desk/query_report.py", line 103, in run
    result = get_filtered_data(report.ref_doctype, columns, result, user)
  File "/home/frappe/benches/bench-2017-05-09/apps/frappe/frappe/desk/query_report.py", line 234, in get_filtered_data
    elif has_match(row, linked_doctypes, match_filters_per_doctype, ref_doctype, if_owner, columns_dict, user):
  File "/home/frappe/benches/bench-2017-05-09/apps/frappe/frappe/desk/query_report.py", line 279, in has_match
    if dt in match_filters and row[idx] not in match_filters[dt]:
KeyError: u'currency'

Total values

[nabinhait]

Use erpnext.get_company_currency(), it does caching. Also, company_currency is evaluated in prepare_data as well, call it only one time