* Keep only one TRegistry object in memory instead of creating a new one in each routine.
* Move out relevant functions and TRegistry object from main to helpers to make them usable globally.
- Fixes bug #271 "F5 shortcut in database tree not working"
- Fullfills rfe #519 "Highlight selected item in tree view when focus is elsewhere"
- Fixes inconsistent expansion state of nodes after refreshing
- Fixes plus sign staying when a db node with 0 tables was selected
- Slightly enhances painting speed within the dbtree
- Removes temporary storage of a rightclicked node (DBRightClickSelectItem). VirtualTree handles its right clicked selection exactly like the left clicked one, which makes makes coding a bit cleaner as we can always use the selected item instead of hacking with the right and left clicked node. On the other side it removes a quite user friendly feature. Well, we can reimplement this feature later, though it's not user UNfriendly currently.
- Reasonably rename the StringList "OnlyDBs" to "DatabasesWanted" and "OnlyDBs2" to "Databases"
- Fetch charsets from collations dataset rather than firing an extra "SHOW CHARSET"
- Move fetching defaultCharset to existing TRY clause. No functionality change, just more consistent.
- Sort all comboboxes with charsets and collations alphabetically
- Leave the responsibility for disabling the comboboxes on old servers to the code rather than to the DFM file.
- Adapt Enabled-property of TLables to the comboboxes they belong to.
