Divided the keystone docs into four categories, depending
upon the usage criteria: general information (which will
be common for all), developer documentation,
user documantation and operator documentation.
Change-Id: I2f5dd41acd9874739accc54c4f4fd69460b58334
Since we're moving all policy into code and documenting it there we
should generate those docs automatically, so they are less likely to
be out-of-date.
Change-Id: If00cd3bcc654a45944c0bc8b3f146c75bd970f9a
partially-implements: blueprint policy-docs