Ability to add tag/context

[xeruf]

For example, when I am practicing a piece of music, I often record multiple versions.
Being able to set a default tag, which would either be a tag on the audio file or simply appended to the name, would alleviate the need to always type the name of what I am currently practicing in the post-recording dialog.

This feature could also used to mark the current place or whatever - it should simply be a text, maybe just a word, remembered across recordings and restarts, which is tacked onto each recording while it's active.

See also #80