Merge branch 'develop'
Use the GUIDs of accounts and transactions as arguments for UI components.
The IDs which were previously used will change whenever records are updated
Added dialog for default currency before creating accounts for the first time
Use default currency when creating default accounts
Fix for creating default accounts after changing currency
Instead of modifying input stream before importing, we update currency in database after importing.

Introduce task delegate for executing tasks on completion of import.
Merge branch 'feature/select_default_currency_on_start' into develop

Fixes #169
Fixes #212
Separate QIF export by currency
QIF export fixup
Re-implements old method of GncXML exports to suppport database migrations from version 1.3.x of the app
handling of export by file sharing
Code refactoring and cleanup

Updated copyright notices
Moved non-translatable strings into own file (should ease comparing string files during translation)
reject non-GncXML in migrationHelper
Bug fix, see code
Merge pull request #221 from fefe982/dev-bug-fix

Fixes crash caused by passing wrong UI argument
add TEMP VIEW trans_split_acct
add temp view trans_extra_info
Export only single currency transacions to QIF
e.getMessage can be null
Merge pull request #224 from fefe982/dev-fix-223

Fix app crash due to null error message