A segfault occurred when nOpacity is not the active skin and the
plugin's setup page was exited.

Fonts assigned in constructor of cNopacityMainMenuItem*.
Therefore SetFont(), SetFontSmall(), SetFontEPGWindow()
and SetFontEPGWindowLarge() can be deleted.

We can return new cNopacity() directly in Start()

Fix debug log in cGeometryManager::SetGeometry(void).
Add debug log in cImageCache::CreateCacheDelayed(void)

config.SetThemeSpecificDefaults(), config.SetThemeSetup(),
config.SetFontName(), geoManager->SetGeometry(),
fontManager->SetFonts(), imgCache->CreateCache() and
imgCache->CreateCacheDelayed() is no longer required here.

config.LoadThemeSpecificConfigs() and config.SetPathes() was moved to
cNopacity::ReloadCaches(void).

In Init() all necessary functions are collected in order to properly
initialize the skin. These functions can then be made private in this
class. This can also simplify cNopacity::ReloadCaches().

- Merge CreateCache(void) and CreateCacheDelayed(void)
and move CreateCache() to cImageCache::cImageCache().
This allows a new instance of imgCache to be created
after configuration changes.

- Eliminate cImageCache::Reload()
cImageCache::Reload() is no longer required.

- Initiate osdLeft, osdTop, osdWidth and osdHeight with 0 in
cGeometryManager::cGeometryManager().

- cGeometryManager::GeometryChanged(void) is renamed
to cGeometryManager::SetOSDSize(void) and merged to set
osdLeft, osdTop, osdWidth and osdHeight to cOsd::*.

The cache is now created via cNopacity::SetOSDSize(void)
when the skin is started for the first time or when
the geometry is changed.

All SetDisplay*() were merged and moved to cGeometryManager::SetGeometry.
So we can delete then all unnecessary funktions.