Feature testing includes indexDB

[#129]
Add "try switch from private browsing to normal mode" message on feature detection failure

[#129]
Include feature detection for websql as it is a valid pouchDB adapter

Also, carry out proper indexedDB detection to cater to firefox private mode
[closes #129]
Fix typo and update text.
Text adjustment
Merge pull request #161 from hivewallet/indexeddb

Handle firefox private mode