Jubler improvement suggestions

[MikeIsOnGitHub]

Dear teras, following a series of suggestion to improve Jubler's usability.

• The "join entries" function, once it has merged adjacent subtitles,
  should also check if the resulting subtitles has empty lines, and if that's the case, delete it;
  plus, if the two lines can be compacted into one; it should do that automatically;

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• Also, it would be nice to have another feature,
  called "Merging Suggestions",
  activated by a shortcut, so that:

If
two adjacent subtitles respect ALL the following conditions:

• they're one right after the other;
• the sum of their lines isn't higher then "Maximum number of lines per subtitles" (by default:2)
• the sum of their length is less then "Maximum duration per subtitle"
  (by default: 7 seconds)

Then

those two should be highlighted with a color that's different than the other possible ones,
so the user can immediately check them and consider whether to merge them or not.

If subtitle 1 could be merged to 2, and 2 could be merged to 3,
then subtitles 1,2 and 3 should all be highlighted.

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• Jubler then should:
  • put "srt" as the default file saving extension, or;
  • remember the last format of file you saved. If you saved a file as an srt, then the next time it should also save the file by default as an srt, unless you specify differently.
    ====================================
• Jubler should communicate with Aeneas (source code on github, executable on request);
  ====================================
• Jubler should communicate with subfixer (https://github.com/chetan-prime/subfixer).
  In particular, one should also be able to use subfixer for:
  a) fixing a whole subtitle file;
  b) fixing individual subtitles;
  c) performing a "perfection check" that checks if ALL subtitles of a given file are compliant with th set guidelines, and if so informs the user that the subtitle file is perfectly compliant with Jubler0s quality controls.
  ====================================
• making Jubler communicate con VLC (and embed the video window into the upper left frame of the preview mode - where now is the parrot)
  ====================================
• In the Preview mode, it would greatly help not to have overlapping subtitles. At the very least, the user should have the option to have them overlappable or not.
  ====================================
• In /Tools/Shift Interval, along with the very interval
  (like, -00:01:25, 643)
  a user might also benefit to enter two reference timestamps
  (like, move from 00:02:50,743 to 00:01:25,100)
  instead of manually calculating the interval between the two.
  ====================================
• In file /Preferences/shortcuts there's an option for "Split... in place proportionally".
  It might come handy to introduce another shortcut that extends the concept across several subtitles. Like, I select subtitle 4 to 6, type a shortcut, and jubler recalculates the timing of each of this three subtitles as a ratio between the number of characters of that individual subtitle on the sum of characters in subtitles 4,5 and 6 (hope it makes sense :).
  ====================================
• Unlike Windows and Mac, in Linux version when you either open or save a file,
  the GTK for browsing the filesystem is still old-fashion
  ====================================
• Packaging an appImage version for ARM processor, that can also run on a Raspberry Pi 4
  ====================================

And that's it. Keep up the fantastic work :)
Michele

[fabriciorsf]

Other suggestions:

1. Don't count non-alphanumeric characters
2. Set by time or by frame