switching main branch to main

[caryoscelus]

with main being new default main branch, it makes sense to switch. current moment seems like a perfect opportunity since there are almost no developers who might be affected by the change. another reason to do this now (i.e. together with the next release) is breaking changes in data directory structure, keeping master out of that merge will ensure users who do blind pulls will not be affected negatively by it

timeline:

• after use git-based versioning, change default data paths, refactor #272 / New directory structure, versioning information and "build" types #276 is considered stable, development will happen in main
• before the next release main becomes official default branch

[bitcoren]

When v0.7.11 release?

[caryoscelus]

@bitcoren when everything is well tested and welcoming experience is improved; depending on feature development it may turn to be time for v0.8 though