Update JS API docs

[letmaik]

https://microsoft.github.io/CCF/master/developers/js_app_bundle.html#globals

• renamed: tables -> ccf.kv
• added: <map>.has()
• added: ccf.strToBuf, ccf.bufToStr, ccf.jsonCompatibleToBuf, ccf.bufToJsonCompatible, ccf.generateAesKey, ccf.wrapKey