#920 Add filter for .csv files

[Michael Pavlyshko]

User should select:
1) Role of each column in file(text column, key column(for example, msgid in monolingal .po) or ignore column)
2) Column divider (, ; tab or user defined divider)
3) Text divider ("text" 'text' or text without brackets)

You can see good .csv implementation in LibreOffice.