BUG: Add SimpleITK_VERSION variable defined after find_package

No SimpleITK_VERSION variables were defined after neither
find_package(SimpleITK) nor include(${SimpleITK_USE_FILE}). The
PACKAGE_VERSION variable is now defined in the version config file
which automatically sets the major.minor.tweak component
variables.

Change-Id: I59ff2e500a56e0400655673ec6d64a80cd5d6ba1
Require SimpleITK major version to match for compatible version

When a version is specified for find_package, it's required that the
major version match. In general versioning schemes changes is the
major version represent a change in compatibility.

Change-Id: Ib6e6a9315d94ff351746d6420ea59f3e2b91ab39
BUG: Specify "Development" component for all headers

Change-Id: Ifa00357c33f2d77d57c910ba64277bdba7f32477
Merge branch 'SIMPLEITK-517_HeaderAsDevelopmentComponent' into release

* SIMPLEITK-517_HeaderAsDevelopmentComponent:
  BUG: Specify "Development" component for all headers

Change-Id: Ia94a1758d8dc2f717fea514ff0186c0ed164e64d
Merge branch 'SIMPLEITK-518_AddVersionVariablesForFindPackage' into release

* SIMPLEITK-518_AddVersionVariablesForFindPackage:
  Require SimpleITK major version to match for compatible version
  BUG: Add SimpleITK_VERSION variable defined after find_package

Change-Id: Ic4aa1ab8bed0dd4465a370462815a81b312ed0da