Intention: converting config structure

[ghik]

Originally reported in https://youtrack.jetbrains.com/issue/SCL-10571

It's good to have a refactoring that will convert flat config structure like

a.b.c = 1
a.b.d = "string"
a.x = true

Into tree:

a {
  b {
    c = 1
    d = "string"
  }
  x = true
}

and vise-versa, but it should leave root key flat:

a.b.c.d=1
a.b.c.e=2

should be converted to:

a.b.c {
  d = 1
  e = 2
}