(WIP) Fix Vector Flipping on Using Tape Tool

[shun-iwasawa]

This will fix #2347
This is WIP, as I think this fix is need to be evaluated regarding the following behavior:
When applying the tape tool with "Join Vectors" and "Smooth" options being on, if the target stroke is a part of some filled region, the result sometimes causes unexpected change of styles used for filling (i.e. the fill color sometimes changes).

I'm not sure if it is acceptable for users, since the current OT already have such behavior when modifying vector strokes.

[shun-iwasawa]

Jenkins

[RodneyBaker]

This PR has passed all tests and appears to be ready to merge.
@shun-iwasawa If this is something I can merge I'd be happy to do it.

I'm doublechecking the WIP aspects of this.
I do confirm this PR fixes the reported issue.

[RodneyBaker]

I agree that this is WIP concerning Fills.
The primary workaround for fills would be to perform the Fill as a step independent of the auto-inbetween.

The added ability to maintain the vector order however is very much on target.

[shun-iwasawa]

@RodneyBaker OK, so let's postpone the inclusion of this. Thank you for your checking!

[RodneyBaker]

Tagged as 'roadmap' and moved to 2019 development cycle.

Note for those in need of this update as a partial fix:
Appveyor releases contains this fix and are available for six months from the time of the appveyor build. This presents users with an option to use the stated fix/enhancement/feature in addition to the official release. As with any developmental build use at own risk and back up important files first before use. For more information on appveyor builds see: LINK

Direct Link to developmental build download: (WIP) Fix Vector Flipping on Using Tape Tool

[RodneyBaker]

Closing temporarily. Will reopen in 2019 development cycle.

[RodneyBaker]

@shun-iwasawa I'm reopening this PR as it found some renewed interest via chat on discord.
Not sure of status but at least the issue can be reviewed and discussed.