0.6.2

App changes

Added an optional Regular Expression that can be tested against a String field in an Entity. Any unmatched character in a string value will just be discarded. This allows the creation of custom field type (that needs to follow some specific pattern), while still having a safety net (the editor cleans up invalid parts).
Fixed missing "world grid size" inputs in Grid Vania layouts. They should now appear in the World panel.
Fixed level creation in "Linear" world layouts that only contain 1 level
Fixed loading of null multiline fields
Fixed a crash on layer removal
Added "internal" (ie. "only for editor use") indicator for undocumented fields in Json
Fixed Json doc typo
Fixed Travis unit tests
Fixed new level creation in "Linear" layouts that only contained 1 level
Minor changes & fixes on Home and Support pages