Add basic cleanup tasks for songs

[bohning]

The tool could perform some basic cleanup/fixes on the songs, e.g.

• replace decimal commas by decimal points in #BPM, #GAP, #PREVIEWSTART, #START
• delete leading line break (after header, before first note)
• delete trailing line break (after last line, before E)
• round #GAP to nearest integer (to nearest 10 ms)
• shift first note to beat 0 (and adjust #GAP accordingly)
• increase low BPM values (all all timings) to be in a sensible range (200 <= BPM < 400)
• decrease (insanely) high BPM values (and all timings) to be in a sensible range (e.g. BPM <= 600?)
• fix line break timings (similar to USDX Editor -> T)
• fix touching notes (shorten earlier note by 1 if duration > 1)
• normalize pitch values (sometimes they are in the 60s --> lowest pitch in [0, 11])
• correct spaces (after each word instead of in front of each word)
• fix empty notes (~?)
• replace accents misused as apostrophes (accents ` and ´ -> ')
• convert relative to absolute timestamps
• round #BPM to 2 decimal digits
• replace upright apostrophe ' by typographer’s apostrophe ’ (optional?)
• capitalize the beginning of each line (similar to USDX Editor -> C, optional?)
• fix overlapping notes (shorten earlier note by overlap + 1 if resulting length >= 1)
• fix zero-length notes (how?)
• ensure medley start and end beats are on note start and end respectively
  If we look for the next note end going backwards, this would also fix a gap introduced by the touching notes fix.
• fix quotes (single 'text', double "text" etc. to “text” or »text« or «text» etc. depending on language)

Advanced cleanup:

• add uploader as #CREATOR (if empty) (add editors, separated by commas?)
• translate language names from other than English to English (see https://github.com/UltraStar-Deluxe/UltraStar-Manager/blob/d0f7e879d856f487ae0abed9d484c615f13ae1ee/src/plugins/preparatory/QUPreparatoryTask.cpp#L314)
• Find suitable medley section automatically (if not present)
• Set preview tag (if not set, to medley start if available, otherwise to time of first beat)
• determine/verify #LANGUAGE (cld2 https://pypi.org/project/pycld2/, cld3 https://pypi.org/project/gcld3/)
• determine/verify #GENRE (e.g. https://www.chosic.com/music-genre-finder/?track=1z3ugFmUKoCzGsI6jdY4Ci or https://www.soundmaximum.com/music-genre-finder/)
• determine/verify #YEAR (e.g. swisscharts.com or last.fm lookup of artist/title)

[DeinAlptraum]

replace upright apostrophe ' by typographer’s apostrophe ’ (optional?)

I would really appreciate if this could be made optional (i.e. allowing to choose the apostrophe you prefer)

[bohning]

I would really appreciate if this could be made optional (i.e. allowing to choose the apostrophe you prefer)

What would you choose and why?

[DeinAlptraum]

I prefer the straight apostrophe ' visually.
I've also had various problems in the past with files with typographer's apostrophe in their name not being recognized by USDX, though it's been a while, but I would prefer to eliminate this source of errors to be sure.

[bohning]

I guess the best option to handle notes of zero length is to extend them to 1 beat duration if there is 2 beats space to the beginning of the next note. What do you think?

[bohning]

How shall we handle txt files without linebreak timings? The syncer could insert linebreak timings (then they would work with the current USDX), or it could consider the linebreak timing optional. Currently, the linebreaks are deleted entirely by the syncer, rendering the file unusable (related: USDX refuses to load files that do not contain a single line break, presumably because songs with a single line of lyrics are rather uncommon, but exceptions exist: https://usdb.animux.de/index.php?link=detail&id=25978, see UltraStar-Deluxe/USDX#895).