firebas write/remove methods

FirebaseReadWrite.java

setValue()        writes/ replces data at the specified path replacig any data 
                  at that path

updateChildren()  write to specific childern of a parent node but without overwriting 
                  other child nodes

push()            add to list of data a. A unique id is generated by push depending 
                  on the timestamp

runTransaction()  used in ase of a counter, when seeralpeople update the same list

removeValue()     allows to remove data ata specfic location