Scripts enhancements

[Utumno]

• internal API for issues needs revamp - problem is how much will go to github_wrapper and how much to html - but as it is it is bad, bad, bad (try generating master changelog)
• cache needs rewrite - I had seen somewhere try except KeyError but lost the page. Anyway (apart from pythonisms I'd like to add) there must be an exhaustive search in existing items to see if we can filter instead of hitting github - but I want to avoid the ifelseheimer - I need some OO trick there
• nexus pages must be autogenerated too issue wrye-bash/meta#14
• get all labels and throw if they are not up to date they won't change this often (edit the main repo Labels wiki too)

Assigning to me but if anyone (Lo ?) wants to lend a patch...

Marking this bug btw just to bump the priority (in this repo makes sense to label bug high priority items and enhancement lower ones)

[Utumno]

Committed some changes to the cache and some changelogs for 305 (to be regenerated) - feel free to improve
I will take care of finally merging the rel-305 branch - but feel free to commit in it - I already rebased it once btw - so be ready to pull and rebase
Btw the milestones in this repo are not strict - if 305 is out we just change the milestone to 306 in open meta issues

[Utumno]

For discussion on gitpython and co see wrye-bash/wrye-bash#103

[Infernio]

@wrye-bash/bashers meta is gone - I merged its history, but none of its files (with the exception of the changelog scripts) into the master branch of this repo. This will allow us to recover files in the (unlikely) event that we do end up needing them, while not actually bothering us during regular development on this repo.