clean up and extend preferences dialog

[zenogantner]

Currently, the preferences dialog is a mess.

It could be cleaned up a bit.

1. remove unnecessary configuration options like

1.1 "use panel order for Ctrl-Tab (not usage history)" - now can be set via keybindings editor
1.2 "default line ending" - would be the platform line ending; setting this to another value should be an advanced option
1.3 "methods order" - should be set directly in outline and function list windows - see #826

2. re-group into logical sets of options (in particular the "Behaviour" tab)
3. Have tooltips for each option that explain the option a bit more.
4. Have context-sensitive "Help" button

Those suggestions are not meant to be absolute, so of course one could argue whether option A should be a preference option or an advanced option.

[zenogantner]

Another thing: One can move through the different option groups using the arrow keys. It would be nice to offer also the possibility to move through the tabs (besides cycling over all elements with the 'Tab' key and then using the arrow keys) by hitting Ctrl-(Shift)-Tab, Alt-Left/-Right, Ctrl-PgUp/PgDown?.

[zenogantner]

The plugin settings should also be accessible from the preferences dialog.