SONAR-5840 It should be possible to specify a negative value on rule parameter of integer type
SONAR-5841 Empty parameter on integer, boolean and float types should be authorized when setting a rule parameter
Merge remote-tracking branch 'origin/branch-4.5'

Conflicts:
	server/sonar-server/src/main/java/org/sonar/server/util/IntegerTypeValidation.java