Share function, button w/ empty icon

- Added an empty share `ImageButton`
- Added the share strings, that will have to be translated
- The Intent for sharing simply sets the weather condition text and some FWeather info
- The FWeather sharing info is contained in a `final String`
- Weather error IDs are now negative, so a quick check can be executed
Added the Share icon assets
Merged 'develop'.

Conflicts:
	res/layout/include_widgetbuttons.xml
Fixed the widget button layout after merging
Merge branch 'feature/18-share-weather' into develop