Support cells with CellMetadata, ValueMetadata, and Phonetic attributes

[dbernheisel]

In the OpenXML spec, there are three additional XML attributes that may be present: cm, vm, and ph. Before this commit, this would raise an error specifying "Unknown attribute".

The Cell Metadata index isn't required for rendering the data within the cell. Neither is Value Metadata. Both of these are for extensions to operate upon the cells.

The cell "Show Phonetic" attribute isn't required either, as it only informs the tooltip the user would see if this is present.

These three additional attributes are now ignored since they don't affect the rendered value.

I tested this using Elixir 1.9.4 and Erlang 22.0.3.

Without the changes, this is what Xlsxir would do when parsing the included fixtures

``` 1) test parses cells with cell metadata successfully (XlsxirTest) test/xlsxir_test.exs:129 ** (RuntimeError) Unknown cell attribute code: {:ok, pid} = multi_extract("./test/test_data/cell-metadata.xlsx", 0) stacktrace: (xlsxir) lib/xlsxir/parse_worksheet.ex:73: anonymous fn/2 in Xlsxir.ParseWorksheet.sax_event_hand ler/4 (elixir) lib/enum.ex:1336: Enum."-map/2-lists^map/1-0-"/2 (xlsxir) lib/xlsxir/parse_worksheet.ex:68: Xlsxir.ParseWorksheet.sax_event_handler/4 (erlsom) .../xlsxir/deps/erlsom/src/erlsom_sax_utf8.erl:1408: :erlsom_sax_utf8.wrap Callback/2 (erlsom) .../xlsxir/deps/erlsom/src/erlsom_sax_utf8.erl:936: :erlsom_sax_utf8.parse ContentLT/2 (erlsom) .../xlsxir/deps/erlsom/src/erlsom_sax_utf8.erl:196: :erlsom_sax_utf8.parse /2 (xlsxir) lib/xlsxir/sax_parser.ex:61: Xlsxir.SaxParser.parse/3 (xlsxir) lib/xlsxir/xlsx_file.ex:93: Xlsxir.XlsxFile.parse_to_ets/3 (xlsxir) lib/xlsxir.ex:89: Xlsxir.extract/4 test/xlsxir_test.exs:130: (test) ...... 2) test parses cells with value metadata successfully (XlsxirTest) test/xlsxir_test.exs:135 ** (RuntimeError) Unknown cell attribute code: {:ok, pid} = multi_extract("./test/test_data/value-metadata.xlsx", 0) stacktrace: (xlsxir) lib/xlsxir/parse_worksheet.ex:73: anonymous fn/2 in Xlsxir.ParseWorksheet.sax_event_hand ler/4 (elixir) lib/enum.ex:1336: Enum."-map/2-lists^map/1-0-"/2 (xlsxir) lib/xlsxir/parse_worksheet.ex:68: Xlsxir.ParseWorksheet.sax_event_handler/4 (erlsom) .../xlsxir/deps/erlsom/src/erlsom_sax_utf8.erl:1408: :erlsom_sax_utf8.wrap Callback/2 (erlsom) .../xlsxir/deps/erlsom/src/erlsom_sax_utf8.erl:936: :erlsom_sax_utf8.parse ContentLT/2 (erlsom) .../xlsxir/deps/erlsom/src/erlsom_sax_utf8.erl:196: :erlsom_sax_utf8.parse /2 (xlsxir) lib/xlsxir/sax_parser.ex:61: Xlsxir.SaxParser.parse/3 (xlsxir) lib/xlsxir/xlsx_file.ex:93: Xlsxir.XlsxFile.parse_to_ets/3 (xlsxir) lib/xlsxir.ex:89: Xlsxir.extract/4 test/xlsxir_test.exs:136: (test) ```

[pierot]

@jsonkenl any chance to get this merged?

[jsonkenl]

@pierot and @dbernheisel Sorry for the delay!

[pierot]

@jsonkenl thanks! I didn't want to pressure you, just reminding :)

[deepfryed]

@jsonkenl any chance you could publish a new version to hex.pm ?