[Bugfix] Activate Unused Colour (#3)

[kevinmatthes]

This Pull Request will activate the currently unused colour base07 from the coulour scheme definition. But it will also require further maintenance of the existing colour schemes.

At the moment, many colour schemes define an arbitrary colour for base07 which was not assumed to be applied. The resulting appearance due to the activation is not always what users might expect. Hence, the fields base04 and base07 of many themes need to be adjusted.

Since this Pull Request is not done, yet, but merely for discussion, I am looking forward for constructive feedback and ideas.

[kevinmatthes]

If activating the colour at all, what should be coloured with? I would like to suggest to apply the colour onto the status bar.

[kevinmatthes]

The colour is unused because of the almost similar names for base01 and base07 in the conversion function: lighter_background versus light_background. Zee's default theme uses indeed base07 for is_not_modified such that activating this would be intended behaviour.

[kevinmatthes]

I just counter-checked all colour schemes. This Pull Request will be an enhancement for all of them since it highlights the very important change status and position (line / column number) fields.

[kevinmatthes]

I am going to squash the submitted commits and to re-submit them in a fresh Pull Request.