Add Page suffix to doxygen page, place in itk::simple namespace

Placing the doxygen pages in the namespace allow for automatic linking
to classes without namespace qualification.

Change-Id: I3e2072298b32e6f88d65af867f8ca10055a97c6e
Add sitk namespace alias on example page.

This enable links from the C++ example to the used classes in the
doxygen.

Change-Id: Iaea442402f0ff27a4a83f1c380ed60a6fab52b72
Adding doxygen page describing Commands and Events

dave's text edits

Change-Id: I7fb700df4d260b1596be3eb95dfe1508d88ce024
BUG: adding missing doxygen comment style for PixelIDValueEnum

Change-Id: I3e81cd81ff5410bcecf11a609cc2527fae4efa6a
linking ProcessObject and Command class to doxygen page

Change-Id: Ib2600293b8514ed93bd8a1e4de7112231ca1a527
Adding Documentation for EventEnum.

Change-Id: Ia372b0b09293e4258874fe4ff20bc7515b860f73
Merge topic 'SIMPLEITK-466_AddDoxygenPageDescribingCommands' into next

e42b96a8 Adding Documentation for EventEnum.
2ce9fca3 linking ProcessObject and Command class to doxygen page
300a98dc BUG: adding missing doxygen comment style for PixelIDValueEnum
3fa284c4 Adding doxygen page describing Commands and Events
d468b810 Add sitk namespace alias on example page.
ec3c90be Add Page suffix to doxygen page, place in itk::simple namespace