#25 Use id3tag for cd number

[Tanyel A. Nimeu]

This patch adds a new input field for the cd number (ID3FID_PARTINSET), which is then written to the id3-tags of mp3 files.
Additionally a new format variable %D is added for using the cd number in format strings.

Based on ripperX 2.7.3
This patch depends on 01-revise-parse_rx_format_string.patch (see patch ID 3167133)
and should be applied with 02-playlist-name-config.patch (see patch ID 3167134)
and 03-albumartist-format-variable.patch (see patch ID 3167138)
and 04-embedded-cover.patch (seed patch ID 3167147)

[Tanyel A. Nimeu]

id3tag for cd number and format variable