Add listAddressbook to api

listAddressbook returns label and address for each address in the
addressbook.
Identicons working in most lists, but not working for new items yet.

There are no settings yet.
Move duplicated sql code into helper
Have API calls use sql helper
Have bitmessageqt use sql helpers
Have helper_inbox use helper_sql
class_singleCleaner uses helper_sql
Merge branch 'master' into sql_refactor
Identicons now in new messages and in the From combobox.

[Broadcast Subscribers] gets the Bitmessage Icon for identification. This is hard-coded now, I would favour to put [Broadcast Subscribers] as a fixed item into the Address Book, so you can set an avatar as soon as i implement avatars.

Still no options yet: There will be an option to disable Identicons and Avatars separately. Another option will be for the suffix (to mimic adresses like "BM-...@bitmessage.ch" or to add a personal "salt" to prevent identicon attacks where someone creates an address with an identicon that looks alike the one of a known address). Also, identicon size (coupled with row height) should be available, but is of low priority.

Next step (after the settings) is to load specific avatars for each address.
use helper_sql for helper_sent
use helper_sql in class_singleWorker
use helper_sql in class_receiveDataThread
have shared.py use helper_sql and move the sql queues and locks to helper_sql
Merge branch 'master' into sql_refactor
new API method needs to use helper_sql
Fix regression where I couldn't add a subscription
Fixed regression in adding to address book
quoted out the BSD licensed code (as i didn't get it to work properly yet)
Merge remote-tracking branch 'upstream/master' into sql_refactor
Added SqlBulkExecute class so we can update inventory without a million commits