Add note that the flowable-rest.war is build by Spring Boot
Add note that the flowable-rest.war is build by Spring Boot

Closes #2939

dbmalkovsky/flowable-engine,dbmalkovsky/flowable-engine,flowable/flowable-engine,flowable/flowable-engine,flowable/flowable-engine,flowable/flowable-engine,dbmalkovsky/flowable-engine,dbmalkovsky/flowable-engine