Allow non-verse headings in between verses

[Castlepool]

Thanks a lot for your efforts to develop this plugin, I really like it!

Two things didn't work for my markdown bible when trying to "Copy Bible verses".
With this pull request I'd like to fix these.

1. Support having headings (of higher level) in between verses

###### 1
1st verse text

## Some helpful heading that is not a verse number

###### 2
2nd verse text

###### 3
3rd verse text

=> Support added by new setting to specify which heading level to search for when copying verses.

2. Support empty line between verse heading and verse text

Because I format my markdown to have an empty line underneath each heading:

###### 1

1st verse text

###### 2

2st verse text

If these cases seem to specific to you, feel free to say so or only use part of it :)

[kuchejak]

Hi, thank you very much for your PR! It is a good addition and it seems to work great.

I have just one small request, could you please change the setting to a dropdown (combo box)? I think it will be a little bit easier to use that way.

[Castlepool]

Hello, thanks for your quick response and feedback. I made the setting a dropdown now, good idea!
(and also fixed a typo in one of the other settings)

[kuchejak]

Looks great, thank you for contributing!