PouchDB.allDbs should return a promise

[neojski]

The same as #1377

[daleharvey]

It should, however taking goodfirstpatch off, we are replacing the allDbs implementation so not particularly worried about fixing this beforehand

[neojski]

Why is enableAllDbs false by default? I need to know allDbs for incremental mapreduce (cleanup issues) or I'd have to keep track of created dbs by myself.

[daleharvey]

The current implementation I wouldnt consider production worthy, having it do fairly complicated things on part of the critical path of opening a database worries me, allDbs starts acting up and opening a database is impossible

I want to take it out, and its replacement isnt supported 100% (implementation in progress in firefox), so I think we need to think about other ways of keeping track (and taking a look at the couch impl)

[daleharvey]

after a bunch of discussion, allDbs got removed, the current implementation was never going to be enabled by default, and this lets us look at the alternative implementations

https://github.com/daleharvey/pouchdb/pull/1477