Instead of fetching all items of a folder at once using
list(folder.items()), we now use a generator and only fetch new messages
on demand when we scroll down.
We added a few new members to the class to make this happen:
- genList generator of Folder.items()
- totalItem total amount of items in the folder
- itemList will keep a list of Item()'s  which are displayed in the gui,
	so we can do fast lookups or easily remove/add items
- data() will now fetch new items from the generator
Merge branch 'master' of github.com:zarafagroupware/zarafa-inspector into performance
Add note about delete()
Add delete support from ICS
Add FIXME
Fix fetching items when a folder contains < 20 items
Refactor addData to use listcomprehension
update comments
Update comments
Fix wrong commit
Add note about generator.send()
- Use xrange instead of range()
- ItemListModel->data() Remove unneeded loop
- ItemListModel->data() Quit early
- Fetch 20 items by default
- Remove old comment
Simplify if statements
Fix wrong if statements
Add comments
Merge pull request #38 from zarafagroupware/performance

Performance