Fixes #2881, NullPointerExceptions when gc.com username is blank

- username, password cache was already removed
- returning empty pair on missing credentials
- cleaning up unneccessary getGcLogin() calls and null checks
fixes #3018 - show progress storing cache for edit personal note
Merge pull request #3046 from marco-jacob/fixStoreForEditPersonalNote

fixes #3018 - show progress storing cache for edit personal note
fixes #3021 - introduce named constants
Merge pull request #3047 from marco-jacob/introduceConstants

fixes #3021 - introduce named constants
Fixes #2988, New settings: Check and Save gc.com login not intuitive any more

- changing log-in info resets the login status and re-initiates log-in on return to MainActivity
Implements #17, Reload reCAPTCHA

Took layout and ideas raised by @culmor30
Moved reCAPTCHA key and challenge retrieval to the RecaptchaReceiver
Added slovenian translation - with fixes, squashed commit
Merge pull request #3048 from jeancaffou/master

Added Slovenian translations
Slovenian translation - fixed lint warnings and missing translations
Fixes #2918, Restore debug info for live map

Added url propagation to Viewport search in connector factory
Tuned debug info
Merge remote-tracking branch 'jeancaffou/master'
Slovenian - small post-merge fix
oc pl WIP