pd-server rc2

• Support location aware replica sheduling
• Conduct fast scheduling based on the number of region
• pd-ctl support more features
  • Add or delete PD
  • Obtain Region information with Key
  • Add or delete scheduler and operator
  • Obtain cluster label information

pd-server rc2-preview

*: update vendor. (#486)

pd-server rc1

*: pid to id (#448)

PD Beta4

server/cache: hide regions in clusterInfo (#367)

* server/cache: hide regions in clusterInfo

regionsInfo will be rewrote later, we should not access it directly.