Add a query to check last "eventid" in Zabbix server.
Add a function to return last "eventid" in Zabbix Server.
Change variable name.

  lastEventId ->
dbLastEventId

Because, I'm preparing to check last "eventid" in Zabbix Server.
So, conventional name cause an accident.
Fix wrong function type.

 int64_t ->
uint64_t
Fix wrong variable type.

 int64_t ->
uint64_t
Change error indication.
Add string type variable "strLastEventId" to store json data.

I think first I can store json data to uint64_t variable.
But, I understood I could not do it.
Add appoint point to start reading json.
Add change from string type to uint64_t type.
Add store last "eventid" in Zabbix Server.
Cancel content of commit in 15cdb37.
Add a new function: convertStrToUint64
Use convertStrToUint64 function to convert string to uint64_t
Fix format designator for uint64_t
Fix wrong format designator for uint64_t
Add constant: UNLIMITED
Add upper limit of eventid when get event.
Change method to get event data from Zabbix Server

This method get event data by dividing.
But, this method isn't good.

For example:
+ When get copious event data, Hatohol can't stop.
+ Event data isn't stored to the database.
  - (I'm resarching this problem)
Use while loop instead of do~while loop.
Move position to call "makeHatoholEvents" function

Because, event data isn't stored imperfect to the DataBase.