Manual section adjustment

[stevenwaterman]

Users should be able to edit the sections and their timings. This has serious implications for the patching system, because if we add a section early on then it will change all the indexes.

Users should be able to:

• Split a section into two (specify a timestamp to split it, have it become two sections)
• Combine two sections (make two sections into one section that covers the whole time of the two it came from)
• Add a section (specify start and end time that doesn't overlap with others)
• Delete a section
• Adjust a section's timings

[stevenwaterman]

This is probably going to be de-scoped because perfect section timing only really matters for subtitles, which isn't a priority as Lexoral moves towards research-focus