Elixir processor should handle more of the ways that a CSV file can contain transparency data.

[Greatlemer]

Description

Be able to read and process CSV files with any number of the following:

• Rows of preamble before the actual header (e.g. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/508397/Prime_Minister_Meetings_with_External_Organisations_October_to_December_2015.csv)
• Alternate ways of labelling the 'Minister' column (e.g. blank first column, "SPAD", "Special Advisor" or "Permanent Secretary")
• Stray punctuation at the start of a date cell (e.g. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/535730/No_10_special_advisers_meetings_january_march_2016.csv)
• Dates with the day of the month as 1st/2nd/3rd etc. (e.g. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/508423/No_10_Special_Advisers_Meetings_with_Senior_Media_Figures_October_to_December_2015__1_.csv)
• Each column represents a month for the minister in question with each row being an org_string - reason pair (e.g. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/412096/sir_jeremy_heywood_external_meetings_apr_jun_2014.csv)
• Alternate ways of labelling the 'Date' column (e.g. 'Month': https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/60753/FINALcopermsecmeetings-jul11-sep11.csv)
• An entry of 'NIL' in the date column to represent no meetings for a given minister (e.g. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/468372/DPM_SpAds_Meetings_July_2014_-_March_2015__1_.csv)
• Data in blocks each headed by a line saying which minister they're for and containing only three columns, one for each of the other fields (date, org_string, reason)