Fix double buttons for great people for constructing great improvements

Fixed custom file directories on Android

Approve values of 0 for certain mod constants in validator - By unciv-loof

By SomeTroglodyte: 
- Fix black outlines for Stat symbols in notifications
- Fix TriggerUponLosingUnit 
- Fix Android on screen keyboard show/hide
- Minor CPU optimization

Add "Vegetation" to Marsh - By EmperorPinguin