Add notices for Budgeted and Actual Expenditure comparison

[otterbotter]

This PR:

• Changes the way we detect if the amount of cells returned is higher than the set limit (looks like a OpenSpending API bug, to be reported)
• ➕ Adds notices to the Budgeted and Actual Expenditure comparison summary section
• ➕ Adds notices to the Budgeted and Actual Expenditure comparison programme breakdown section
• ➕ Adds two new test cases, for a total of 7 new tests.

Notices appear for the summary section when:

• Data has not been published (total for a given year is empty)
  -- E.g. Please note that the data for 2014, 2013 and 2012 has not been published on vulekamali.
• A department did not exist for at least one year. (total for a given year is > 0, but no data for this dept in this year)
  -- E.g. This department did not exist for some years displayed.

A notice appears for the programme breakdown section when:

• Any programme in any year is missing data for all 4 phases.
  -- One or more programmes did not exist for some years displayed.

Notices are presented as a list of strings in the top level of the YAML output, e.g.:

  notices: ['This department did not exist for some years displayed.']
  programmes:
  - items: ...

📓 Notes:

• A bug was found in the OpenSpending API and an issue was opened

[jbothma]

nice - I've been thinking and googled a bit around conventions for this - did you just decide to do it this way or is this a convention you found somewherE?