SSDM-13251: switched lib-transactional-file-system to use lib-json library

...ce/java/ch/ethz/sis/afsjson/jackson/JsonObjectMapper.java

lib-transactional-file-system/build.gradle

lib-transactional-file-system/settings.gradle

...n/java/ch/ethz/sis/afs/manager/TransactionConnection.java

...main/java/ch/ethz/sis/afs/manager/TransactionManager.java

...le-system/src/main/java/ch/ethz/sis/afs/startup/Main.java

...c/main/java/ch/ethz/sis/shared/json/JSONObjectMapper.java

...ava/ch/ethz/sis/shared/json/jackson/JSONObjectMapper.java

.../ch/ethz/sis/shared/json/jackson/JacksonObjectMapper.java

...onal-file-system/src/main/resources/afs-config.properties

...-system/src/test/java/ch/ethz/sis/afs/AFSEnvironment.java

...hz/sis/afs/manager/AbstractTransactionConnectionTest.java