rename more occurrences of mode to severity

src/main/java/org/caosdb/server/database/proto/Rule.java

src/main/java/org/caosdb/server/jobs/Job.java

src/main/java/org/caosdb/server/jobs/JobConfig.java

...in/java/org/caosdb/server/jobs/core/CheckDescPresent.java

...in/java/org/caosdb/server/jobs/core/CheckNamePresent.java

.../server/jobs/core/CheckNoAdditionalPropertiesPresent.java

.../org/caosdb/server/jobs/core/CheckNoOverridesPresent.java

...a/org/caosdb/server/jobs/core/CheckParOblPropPresent.java

...ain/java/org/caosdb/server/jobs/core/CheckParPresent.java

...in/java/org/caosdb/server/jobs/core/CheckPropPresent.java

...in/java/org/caosdb/server/jobs/core/CheckUnitPresent.java