[Cmake] Some changes in CMake

[Andy Cedilnik]

Hello,

While working on GUI, I did not like the way advanced variables are
implemented inside cmake, so I modified it a bit. Now the "right" way of
accessing cache values is through cmCacheManager::CacheIterator. So, for
example if you want to access cache variable, you say to cache manager:

cmCacheManager::CacheIterator it =
cachem->GetCacheIterator("SOME_VARIABLE");

Then you can get/set value, help etc on the it, for example:

it.SetValue("Value");

The second thing is I added properties to cache entries. For now there
are only two properties, help string and advancness of the variable. To
access properties, you can use:

it.SetProperty("ADVANCED", false);

This way when we add other properties to cache variables, we do not have
to add any new API.

I fixed GUIs to work with the changes. Please let me know if there are
any problems.

				Andy